1)
х/3+х/4=-21
4х/12+3х/12=-21
7х/12=-21
7х=-21×12
х=-3×12
х=-36
2)2m/3-4m/5=3
10m/15-12m/15=3
-2m/15=3
-2m=3×15
m=3×(-7,5)
m=22,5
