First, let's define the variables d and q as follows:
d: total number of dimes
q: total number of quarters.
"Joan has an equal number of dimes and quarters" means that d=q.
"...with with a total value of $1.40" means that
0.1 d + 0.25 q =1.40. ***
This is because Joan has a total of d dimes each with a value of 0.1$, and a total of q quarters, each with a value of 0.25.
Since d=q, we can write the equation *** as:
0.1 q +0.25 q=1.40
0.35 q=1.40
q=1.40/0.35 = 4.
Thus, Joan has a total of 4 quarters, and 4 dimes.
Answer: 8 coins.
