1.(a:7+4)*8-14=50
(a:7+4)*8=50+14
(a:7+4)*8=64
a:7+4=64:8
a:7+4=8
a:7=8-4
a:7=4
a=4*7
a=28
2.(39-a:7)*40-48=9
(39-a:7)*40=9+48
(39-a:7)*40=57
(39-a:7)=57:40
39-a:7=1,425
a:7=39-1,425
a:7=37,575
a=263,025
3.62+(36:6-9*6):a-6*8=20
62+(36:6-9*6):a-6*8=20
62+(6-54):a-48=20
62+(6-54):a=20+48
62+(6-54):a=68
(6-54):a=68-62
(6-54):a=6
-48:a=6
-a=48:6
-a=8
a=-8
4.(131-67):c-(5*6+10):8+87=100
64:c-(30+10):8+87=100
64:c-40:8+87=100
64:c-5+87=100
64:c=100+5-87
64:c=18
c=64:18
c=3,(5)