SOLUTION
STEP1: write out the equations 

STEP2: From the first equation, make x the subject of formula

STEP3: Substitute the expression for x into equation 2 and 3
for equation 2, we have 

 Then for equation 3, we have 

STEP4:Simplify each of the expression above 

Similarly for the equation obtain for equation 3, we have 

Step5: Write y interm of z

Step6: subsitute the expression for y into the equation for x in step 2

Therefore 
