<PRE><B>Question 1079717</B>
Let the $6 books be x and the books at 6.50 y:
So we have:
x + y = 9 subtract y from both sides:
x = 9 - y
:
6x + 6.50y = 56 substitute for x
6(9 - y) + 6.50y = 56
54 - 6y + 6.50y = 56
0.50y = 2
y = 4
So the student got 4 books at 6.50 and 9 - 4 = 5 books at 6.
:
Check:
4 × 6.50 + 5 × 6 = 56
26 + 30 = 56 Correct.</PRE>