Find the 20th term in the arithmetic sequence 15, 21,

129

Step-by-step explanation:

The difference between 15 and 21 is 6, and that between 21 and 27 is also 6.  Thus, the common difference is 6 and the first term is 15.

The rule for calculating the nth term of this sequence is therefore

a(n) = 15 + (n-1)6

Check:  Is the third term 27 when n = 3?  Is a(3) = 15 + (3-1)6 = 27?  yes.

Thus, the 20th term is

a(20) = 15 + 19(6) = 129

the answer would be c:   ax + b = ax + c

step-by-step explanation:

n=9

step-by-step explanation:

7 times a number = 7n

decreased by 13 = 7n-13

same as is =

5 times the number = 5n

increased by 5 = 5n+5

7n-13 = 5n+5

2n=18

n=9