Explanation:
C = cost of a composition book; 5 composition books purchased
T = total amount spent < $26
M = cost of magazine = $4
T = M + 5C < $26
$4 + 5C < $26
The problem statement did not ask for a solution, but here it is:
$4 + 5C < $26 ⇒ 5C < $22 ⇒ C < $4.40
Cost of a composition book < $4.40