[420-3·(103-345:15):12]-5·75<25[420-3·(103-23):12]-375<25
[420-3·80:12]-375<25
(420-240:12)-375<25
(420-20)-375<25
400-375<25
25<25 fals pt ca 25=25
2). a)3x+20=x+60
3x-x=60-20
2x=40
x=40/2
x=20
4). Aflati 4 numere naturale consecutive stiind ca impartind suma lor la 5 obtinem catul 8 si restul 2.
nr.consecutive sunt:a,a+1, a+2, a+3
a+a+1+a+2+a+3=x
x:5=8 rest 2
x=5·8+2
x=42
a+a+1+a+2+a+3=42
4a+6=42
4a=42-6
4a=36
a=36/4
a=9
deci nr.consecutive sunt:9,10,11,12
9+10+11+12=42