Question

Suppose y varies jointly with x and z, and x = 4 when y = 8 and z = -2.What is the value of x when y = 12 and z = 3?

Answer 1

Varies jointly or directly (same thing) means you have the equation of y = kx. In this case, though,y varies jointly with x and z, so you have y = kxz. The first job is to find k, which you will solve for by plugging in the first 3 numbers given. Once you find k, you can plug in the final numbers to solve for x.

Answer 2

@Psymon