решите уравнения!
1)1/3x+1/5x+1/6x+21/40
2) 5 1/4x-2 2/3=1 5/12

1)1/3·х+1/·х+1/6·х+21/40=2/6·х+1/6·х+1/5·х+21/40=3/6·х+1/5·х+21/40=
=15/30·х+6/30·х+21/40=21/30·х=21/40
21/30·х=-21/40
х=-21/40 : 21/30=-21/40 · 30/21=-3/4

2) 5 1/4·х-2 2/3=1 5/12
21/4·х-8/3=17/12
21/4·х=17/12+32/12=49/12
х=49/12 : 21/4=49/12 · 4/21=7/9