Answer:
3 paperback books
Step-by-step explanation:
Let the number of paperback Kate bought be a and the number of hard books be b.
Given that she bought 5 books then
a + b = 5
Also, If Kate paid 7d dollars then
a * d + b * 2d = 7d
Divide through by d
a + 2b = 7
Hence we have 2 equations
a + b = 5
a + 2b = 7
subtract the first from the second
2b - b = 7 - 5
b = 2
since
a + b = 5
a + 2 = 5
a = 5 - 2
= 3
Recall that the number of paperback she bought is a hence this is 3
