## Intermediate Algebra for College Students (7th Edition)

$n=\dfrac{L-a}{d} +1$
Subtract $a$ to both sides to have: $L-a=(n-1)d$ Divide $d$ to both sides to have: $\dfrac{L-a}{d} = \dfrac{(n-1)d}{d} \\\dfrac{L-a}{d} = n-1$ Add 1 to both sides to have: $\dfrac{L-a}{d} +1 = n \\n=\dfrac{L-a}{d} +1$