find the constant variation and the equation of variation given that y varies jointly as x and z.

1.) y=16 when x =2 and z = 4

2.) y=10 when x 5/3 and z =6

3.) y= 8 when x=5 and z = 2/5

4.) y=10 when x=0.5 z =4

5.) y= 5/3 when x=5/4 and z=8
Answer this pls.​