0.4(0.9-5/7x)-0.9(0.4-1.3/7x)= 0.40.9 - 0.45/7x - 0.90.4 + 0.91.3/7x= 0.36 - 0.2857x - 0.36 + 0.117x= -0.2857x + 0.117x= -0.1687x
0.4(0.9-5/7x)-0.9(0.4-1.3/7x)
= 0.40.9 - 0.45/7x - 0.90.4 + 0.91.3/7x
= 0.36 - 0.2857x - 0.36 + 0.117x
= -0.2857x + 0.117x
= -0.1687x