Find an equation of variation in which y varies jointly as x and z, and y = 18 when x = 2 and z = 9.

**Solution:-**

Since y varies jointly x and z, use the form y = k * x * z.

To find the variation constant, substitute 18 for y, 2 for x, and 9 for z.

18 = k*2*9

Solve for k.

18 = 18k

1 = k

There variation constant is 1.

The equation of variation is y = x*z.