exam Maths Puzzle Numerical Ability

Umm i dont understand how to do this problem at all and my teacher doesnt give help after class.
(4m^2-5m-6)+(3m^2+8m+9)

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exam Other Question

(x2 - 3X +2) - (3X2 - 5X -1) =
the demand and supply equations for a certain item are given by
d=-5p+40
S=-p^2+30p-8

Find the equillibrium price

A)1.43
B)1.57
C)1.71
D)1.29