(720+е)х 501= 365 730,
720+е=365 730:501,
720+е=730,
е=730-720,
е=10
проверка (720+10)*501=365730, 365730=365730
5t+30-2t=42,
3t+30=42,
3t=42-30,
3t=12,
t=12:3,
t=4,
проверка 5х4+30-2х4=42, 42=42
36*(х-3)=10-2*(х+2),
36х-108=10-2х-4,
36х-108=6-2х,
36х+2х=6+108,
38х=114,
х=114:38,
х=3,
проверка 36*(3-3)=10-2*(3+2), 0=0