Let's make two variables, y(your money) and b(brother's money).
The first sentence creates the equation y-5 = b+5
Rearranging this equation gives me y=b+10.
The second sentence creates the equation y+25 = 2(b-25).
I can plug in y from the first equation, giving me (b+10)+25=2(b-25), which simplifying gives b+35=2b-50, which b=85, so your brother has 85 dollars.
We can check by plugging b in, getting the y value, then plugging it into the other equation.
y-5=85+5 so y=95
Plugging y=95 and b=85 into the second equation, I get 95+25=2(85-25) which is 120=120, which is true, meaning that I solved everything correct.
So your brother currently has 85.