35? a+ 29?a+105:7-415=6000 / +415
35? a+ 29?a+15=6415 /-15
35? a+ 29?a=6400 ⇒ a=5 3505+2905=6400
12) a+(a+1)+(a+2)=4371
3a+3=4371 /-3
3a=4368 /:3
a=1456 R. 1456, 1457, 1458
13) A-varsta Anei, E-varste Elenei, I-varste Inei
A+E+I=91 (ani) E=A/3, I=A×3 ⇒
A+A/3+3×A=91
A/3+4A=91 A/3+12A/3=91
13A/3=91 A=(91×3)/13 A=21 ani
E=21:3 E=7 ani
I=21×3 I=63 ani
Verificare: 21+7+63=91