Question

Which value of y would make OP || LN ?

Answer 1

Remark
All you need do is assume the small triangle is similar to the large one. MO:ML :: MP:MN must be solved.

Givens
MO = 28
ML = 28 + 14
MP = y
MN = y + 18

Equation
28:28+14 :: y: y + 18

Solve
28/42 = y / (y + 18)
28*(y + 18) = 42y        Remove the brackets
28y + 18*28 = 42y
28y + 504 =  42y         Subtract 28y from both sides.
504 = 42y - 28y
504 = 14y                    Divide by 14
504/14 = y
y = 36