a, X : 3 x 48 + X : 4 x 36 = 1500
X x \(\dfrac{1}{3}\) x 48 + X x \(\dfrac{1}{4}\) x 36 = 1500
X x 16 + X x 9 = 1500
X x ( 16 + 9 ) = 1500
X x 25 = 1500
X = 1500 : 25
X = 60
b, X + 7,5 x X : 5 + X : 2 x 9 = 315
X + 7,5 x X x \(\dfrac{1}{5}\) + X x \(\dfrac{1}{2}\) x 9 = 315
X + X x 1,5 + X x 4,5 = 315
X x ( 1 + 1,5 + 4,5 ) = 315
X x 7 = 315
X = 315 : 7
X = 45