Question

When you subtract one square number from another the answer is 7 what are the two numbers?

Answer 1

Let x be first number and y- second number. When you subtract first square number from second you get $y^2-x^2$ and it is equal to 7.

Hence
$y^2-x^2=7$.

Find factors of right and left sides:$(y-x)(y+x)=1\cdot 7$.

Since $y+x\ \textgreater \ y-x$ you have that  
$\left \{ {{y-x=1} \atop {y+x=7}} \right.$.
Add these equations: 
$y-x+y+x=1+7, \\ 2y=8, \\ y=4$.
Then x=7-y=7-4=3.
Answer: $4^2-3^2=7.$

Answer 2

You can get seven from substracting 16 and 9. We know that 16 = 4² and 9 = 3², so what you're looking for is 4² - 3² = 7.

I hope it will help you :-)