x + y = 9
5x + 2y = 30
Step-by-step explanation:
We're trying to find the number of sandwiches and bottles of water he buys and we know he bought 9 in total. This can be represented by x + y = 9 (since x represents the sandwiches and y represents the water). Knowing this, we know that sandwiches (x) cost 5 dollars and water (y) costs 2 dollars. We know he spent a total of 30 dollars. The second equation can therefore be represented by 5x + 2y = 30.