Question

the 16th term of an arithmetic sequence is -8 and the first term is 12. what is the common difference, d?

Answer 1

So the first term a=12
 the formula for arithmetic sequence is 
xn=a +d(n-1)

x16th= 12+d(16-1)=-8
12+15d= -8
15d = -8-12
d=-20/15= -4/3
the common difference is d =-4/3