Respuesta :

40$ - 100% (full price)

x$ - 70% (100-30=70%)

40 * 70 = 100x

2800 = 100x

x = 28

Answer 28$

or

40$ = 100%

then 1% = 40/100 = 0.4$

so 70% will be 0.4 * 70 = 28$