Question

5th term of an ap is 26 and 10 th term is 51 determune its 15th term

Answer 1

a5=26
a+4d=26 (1)
now,
a10=51
a+9d=51 (2)

Subtract 1 and 2
(a+4d)-(a+9d)=26-51
a+4d-a-9d=-25
-5d=-25
d=5
now, put value of d in eq1
a+4d=26
a+4×5=26
a+20=26
a=26-20
a=6
now,
a15=a+14d
a15=6+14×5
a15=6+70
a15=76

hope this answer will help you.