Given expression in the question, x3+3y−3 putting the value of x=1 13+3y−3=7 ⇒3y−2=7⇒y=3 Again putting the value of x=2 in the expression 23+3y−3=20 ⇒3y+5=20⇒3y=15⇒y=5 similarly when x=5,y=11 ∴ Fifth value of expression is 53+3.11−3=125+33−3 =125+30=155