(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