[Video] Q19: A food truck sells salads for $6.50 each and drinks for $2.00 each. the food truck’s revenue from selling a total of 209 salads and drinks in one day was $836.50. how many salads were sold that day?

Explanation for Question 19 From the Math (Calc) Section on the Official Sat Practice Test 1

So for number 19, we can tell that this is a systems of equations 2 problem first off, because we can come up with two variables, 3 right? We can think about as being the number of salads and D being 4 the number of drinks. So we have two variables. 5 That's a clue that we want to systems of equations. 6 And then finally, they've given us two types of information, 7 right? We have the information related to the exact number of items sold, 8 but we also have the amount of money that they made. 9 So with those two types of information, two variables, 10 we can write two really good equations. So the first thing we can see 11 is that they sold a total of 209 drinks. 12 So if S is my number of salads and D as my number of 13 drinks, I should be able to add those together and get 14 209. 15 And now the other equation I can use to show how much total 16 money they made, right? For each salad, 17 they're selling it for six 50. So six 50 times S the 18 number of salads would show me the amount of money that they made from 19 salads alone. And then each drink was sold for $2. 20 So two times the was show me the amount of money that they made 21 from drinks. And if I add those together, 22 I'll get the total amount of money that they made, which was 8 30, 6 0.5. 23 So now I have these two equations here, and I know I want the 24 number of salads, so I want to solve for S so first thing I 25 can do is take that topic equation, 26 solve it for D and then plug D into my bottom equation so...