Answer
0.85X + 52.50
Step-by-step explanation
Let the amount before tax exempt expenses and taxes are removed = X
This is the gross pay. 
Tax deducted = 15% of (X - 350)
 = 15/100 × (X - 350)
 = 0.15(X - 350)
 = 0.15X - 52.5
Take away home = X - (0.15X - 52.5)
 = X - 0.15X + 52.5
 = 0.85X + 52.50