(x+7)÷1又1/5 =6.4
(x+7)÷6/5 =64/10
x+7=64/10 * 6/5
x+7=384/50
x=192/25 -7
x=17/25
x-x4/9=4.5÷2又七分之一
x-4/9*x=45/10 ÷ 15/7
(1-4/9)x=45/10 * 7/15
5/9 *x=21/10
x=21/10 * 9/5
x=189/50