Math Problem Equation

Question

Can you guys solve this Math problem

Harry's store makes a profit of $3 on each economy model drill it sells, and $4 profit on each deluxe model drill. in one week the store made a profit of $84 on the sale of drills . seven more deluxe drills were sold than economy drills . how many deluxe drills were sold during that week?

Answer 1

We know the number of $3 drills times 3, plus, the number $4 drills times 4 equals $84:

3x + 4y = 84

We know that 7 more $4 drills were sold than $3 drills, so the number of $4 drills equals the number of $3 drills plus 7:

y = x + 7

Now that we have two equations, we can solve for two variables:

Plug in (x + 7) for y in the first equation:

3x + 4(x + 7) = 84

Solve for x:

3x + 4x + 28 = 84

7x = 56

x = 8

Now plug in the value of x into either equation to solve for y:

y = 8 + 7