70-15+х=81
х=81-70+15
х=26
------------------
(70-15)+26=81
55+26=81
81=81
х-32-17=35
х=35+32+17
х=84
-----------------------
84-(32+17)=35
84-49=35
35=35
9187 - z : 409 = 7819
z:409 = 9187 - 7819
z:409 = 1368
z=1368 х 409
z= 559512
5x-0,2x=3,2+7
4,8х=10,2
х=10,2:4,8