1) х+(5 4/21-2 3/14)=4,5
х+(109/21-31/14)=4,5
х+(219/42-93/42)=4,5
х+126/42=4,5
х+3=4,5
х=4,5-3=1,5
2) 1 5/18-6=2,1-1 8/9
3) (а-1:2)+5:6=1 5/12
а-1/2 +5/6=17/12
а=17/12+1/2-5/6
а=17/12+6/12-10/12
а=13/12=1 1/12
4) t-(8 3/7+2,8)=7,2
t-(59/7+14/5)=7 2/10
t-(295/35+98/35)=7 1/5
t-393/35= 36/5
t=36/5+393/35=252/35+393/35=645/35 = 129/7=18 3/7