7.If 18, a, b, - 3 are in A. P., then a+b = ? (1 Point)

1212

1515

1616

1111

please give the answer as fast as you can

please

15

Step-by-step explanation:

General terms in AP

f, f+d, f+2d, f+3d, ....  , where f= first term and d= common difference.

The given A.P. : 18, a, b, - 3

here, f= 18    

Put f= 18 in (iii) ,

Put f= 18 and d= -7 in (i) and (ii) , we get

Now,

Hence, the correct answer is "15".