Let x and y be directly related such that y = 9 when x = 3. Find y when x = 7.

Question

Solve. In the space provided, type the answer without any spaces between the letters, numbers, or symbols.

Answer 1

If y is directly proportional to x, then y = kx with k as the proportionality constant.

The given information tells us that

k = y/x =9/3 = 3

Then when x = 7 y = 3(7) = 21