1.
设这个数为x
2x*5/12-3*1/4=1/2
5/6*x=5/4
x=3/2
2.
设乙数为x
(1+15%)*x-x=57.51
0.15x=57.51
x=383.4
算术方法:
57.51÷15%=383.4