设小聪今年X岁9X-7.5X=61.5X=6X=6/1.5X=4小聪今年4岁
解:设小聪今年x岁，得方程:9x一7.5x=6，x=4
解：设小聪为x岁9x-7.5x=6 1.5x =6 x=4
9×4=36爸爸36岁36÷9=4小聪4岁36一6=30妈妈30岁30÷7.5=4小聪4岁
