1.27×26分之25=（26+1)(26-1)/26=(26^2-1)/26=26-1/26=25又25/26
2.3.5×1又4分之1+1又2分之1÷5分之4=3.5*5/4+3/2/(4/5)
=(3.5+1.5)*5/4=6.25
3.（7分之65-9分之65）÷（7分之5-9分之5）=65(1/7-1/9)÷[5(1/7-1/9)]
=13
4.2.5×0.25×1600=2.5×0.25×4×400=2.5×4×0.25×400=10×100=1000
5.4.8×25=(4+0.8)×25=4×25+0.8×25=100+20=120
解方程：
1.26/5-2(x-4)=5
2(x-4)=1/5
x-4=1/10
x=4又1/10
2.3×(x+0.9)=5×(x-17/10)
3x+2.7=5x-17/2
2.7+8.5=2x
x=5.6