设肥皂每块x元,毛巾每条y元.
3x+4y=52.8 ①
5y-3x=41.7 ②
①+②
3x+4y+5y-3x=52.8+41.7
9y=94.5
y=10.5
x=(52.8-10.5*4)÷3=3.6
y-x=10.5-3.6=6.9