Question

What is the common difference of an AP in which $a_{27}-a_7=84$

Answer 1

Let a is the first term and d is the common difference of an AP
27th term = a + ( 27 -1)d = a + 26d
7th term = a + (7 -1)d = a + 6d

now,
a +26d -a -6d = 84

20d = 84

d = 4.2 ( answer)