Question

HELP!!!!
Determine the equation of joint variation. Then solve for the missing value.

x varies directly with y and z.
x = 40 when y = 10 and z = 20.
Find x when y = 30 and z = 40.

Answer 1

x = kyz

plugging in
40 = k*10*20
k = 40/200 = 1/5

equation : x = yz/5

plugging in
x = 30*40/5 = 240

answer: 240

Answer 2

Thank you very much!!!!