Cole can use the fomrula c=3.99n to find the cost c of buing n notebooks . if Cole has $15 to spend, which is a reasonable range for c=3.99n?
c ≥ 3.99n
15 ≥ 3.99n
Divide both sides by 3.99.
3.76 ≥ n
15 ≥ 3.99n
Divide both sides by 3.99.
3.76 ≥ n