12又3/4÷1又1/5+5.25×5/6=?

问题描述:

12又3/4÷1又1/5+5.25×5/6=?
139×137/138+137×1又1/138=?

=139x137/138+137x139/138
=139x137x2/138
=(138+1)(138-1)x2/138
=(138-1/138)x2
=276-1/69