

Let first term of AP = a
Last term of AP = l
common difference = d
number of terms in AP = n
nth term in AP = a + (n-1)d
So 22th term = a + (22-1)d = a + 21*d (Given n =22)
Given that
22th term = 149
=> a + 21*d = 149
=> a + 21*7 = 149 (Given d = 7)
=> a + 147 = 149
=> a = 149 - 142
=> a = 2
Now sum of AP = (n/2)*{2a + (n-1)*d}
=> (22/2)*{2*2 + (22-1)*7}
=> 11*(4 + 21*7)
=> 11*(4 + 147)
=> 11*151
=> 1661
So first terms in AP is 2 and sum is 1661
