A food truck sells salads for 650 each and drinks for $2 each, the food trucks revenue from selling a total of 209,000. drinks in one day was 836 and 50 cents. That looks like a really good business that I might actually think about doing. Selling sells interest. All right, anyway. So they're asking you for how many salads were sold that day. So really, what you want to do is you want to recognize right away that you're dealing with two sets of variables, salads and drinks.

And when you have two variables and you try to know one of them, you want to set up two sets of equations, right two variables, two equations. And the equations that we can have are the following. We can say well, they told us that in one day they sold a total of 209 cells and drinks so I will say s for solids plus d for drinks and we have a total of two 109 now my second equation is going to be what it's going to be the number of salads times the number, the cost of a salad plus the number of drinks times the cost of a drink and total that should be 136.5. So we have 650 s, right, plus $2 or two D, and that should be equal to 136.5 or 136 and 50 cents. Alright, so now that we have two sets of equations, they want us to know how many cells are you really just solving for S. Now one way you can do this is by isolating SM display in this equation to get 209 minus d, plug that value in for this S and then solve it.

But there's actually an easier way that I that I want to show you, and that way is you can actually multiply this whole thing by too. So when you do that, what you'll get is two s plus two D, and that would be equal to 418. Now why did I do this? Because if I subtract this from this, what will I get? Watch this two s, so minus two s plus two D is equal to 480. And if I subtract this whole thing, I will get the following.

I will get 4.5 s and two d minus two D, well that's just zero. So I got rid of that. And that is equal to 136.5 minus 418. That's just gives me 418 point five and see how much better My life is. Now I have my variable s, which is cells, which is what I want to know. And I can solve for that easily by doing 418.5 divided by D 4.5, which gives us 93.

So they sold 93 total salads that day. Now this is a really easy way where you want you can recognize right away that your second equation, you really just want to be left with your salads and none of your drinks. So to get rid of this, you just multiply the other equation, which in this case happens to be the first one by the number that would allow you to cancel out the second term which happened to be two in the first one. Hopefully that makes sense.