1)x=y+72
(x+y);(x-y)=5 rest2
(x+y)=5(x-y)+2
x+y=5x-5y+2
x-5x+y+5y=2
6y-4x=2
6x-4(y+72)=2
6y-4y-288=2
2y=2+288
y=290/2
y=145
x=y+72=145+72
x=217
2a)x:13=1, rest1
x=13·1+1
x=14
x:13=2 rest 2
x=13·2+2
x=28
x:13=3 rest3
x=13·3+3
x=42
deci nr.sunt:14,28,42,84,168,3216...............
b)x;15=1 rest2
x=15+2
x=17
x:15=2 rest 4
x=15·2+4
x=34
x:15=3 rest6
x=15·3+6
x=51
x:15=4 rest 8
x=15·4+8
x=68.................
c) x:8=5
x=8·5
x=40