For this case we propose a system of equations:
x: Let the variable representing the number of math problems result
y: Let the variable representing the number of pages read
According to the statement data we have:

Substituting the second equation into the first we have:

So, Joshua solved 7 math problems.
On the other hand we have:

So, Joshua read 14 pages.
Answer:
Joshua solved 7 math problems and read 14 pages.