notam cu "a" al doilea numar
primul e [tex] \frac{a+21}{2} [/tex]
al treilea e a+10
[tex] \frac{a+21}{2}+a+a+10=98 [/tex]
[tex] \frac{a+21}{2}+ \frac{2a}{2}+ \frac{2a}{2}+ \frac{20}{2}= \frac{196}{2} [/tex]
a+21+2a+2a+20=196
a+2a+2a=196-21-20
5a=155
a=155:5
a=31 al doilea numar
[tex] \frac{31+21}{2}=26 [/tex] primul numar
31+10=41 al treilea numar
