Răspuns :
1.a
2.a+1
3.a+2
4.a+3
4a+6=90
4a=90-6=84
a=84/4=21
1.21
2.21+1=22
3.21+2=23
4.21+3=24
21+22+23+24=43+23+24=66+24=90
2.a+1
3.a+2
4.a+3
4a+6=90
4a=90-6=84
a=84/4=21
1.21
2.21+1=22
3.21+2=23
4.21+3=24
21+22+23+24=43+23+24=66+24=90