john runs .5 miles per day. if he increases .5 miles a day, how many days until he reaches 7.5 miles?

Answer 1

.5 + .5d = 7.5

Solve for d.

Answer 2

.5 , 1 , 1.5 , 2.0 , 2.5
is
.5 , 1.5 3.0 , 5.0, 7.5 on day 5

of course this is an arithmetic sequence with d = .5

Answer 3

http://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html

Answer 4

a + (n-1)d
.5 + (n-1).5