Question 4106
Let A = cost of 1 apple.
Let P = cost of 1 pear.
Let (Or) = cost of 1 orange.

(1)  3A = 4P  So, P = (3/4)A   Substitute into (2) below.
(2)  3P = 2(Or)   

 (2a) 3(3/4)A = 2(Or)  Divide both sides by 2.
             (Or) = (9/8)A    Multiply both sides by 72.
         72(Or) = 72(9/8)A  
         72(Or) = 81A

So, 81 Apples cost the same as 72 Oranges.