Answer:
Number of red squares used are 79.
Explanation:
Given that Adam had used 84 white squares.
White squares used are 20 more than that of yellow.
Let yellow squares used =

(
+ 20) is the number of white squares used.
Also given that 15 more red than yellow
So, Number of red squares used =

To find:
Number of red squares that Adam used.
Solution:
As per given statement:
White squares used =

Number of yellow squares used,
= 64
Number of red squares =

So, Number of red squares used are 79.