1. x-6/25=4/15

x=4/15+6/25

x=(20+18)/75

x=38/75.

2. 7/8-х=1/6

x=7/8-1/6

x=(21-4)/24

x=17/24.

3. 19/40-х=21/50

x=19/40-21/50

x=(95-84)/200

x=11/200.