X-5X%=17.5 7X+5×0.7=83X÷5=48 40-X=3.

X-5X%=17.5 7X+5×0.7=83X÷5=48 40-X=3.

(1)X-5X%=17.5,   (1-0.05)X=17.5,         0.95X=17.5,   0.95X÷0.95=17.5÷0.95,         ...