3.9×7.6+3.9×34-3.9=3.9×（7.6+3.4-1）=3.9×10=39
=3.9×（7.6+34-1）=3.9×40.6=158.34我觉得你好像少打了一个小数点，应该3.4吧，3.4的话应该是39
3.9x7.6+3.9x34-3.9=3.9x(7.6+34-1)=3.9x40.6=3.9x(40+0.6)=156+2.34=158.34
