Alexandra,
Let
G = length of Golden Gate Bridge
B = length of Brooklyn Bridge
From the 1st sentence, we have
G = B + 2064
From the 2nd sentence
G + B = 5796
Let's substitute the expression for G into the 2nd equation.
B+2064 + B = 5796
2B + 2064 = 5796
2B = 3732
B = 1866
and
G = 1866 + 2064 = 3930
The Golden Gate Bridge is 3,930 feet long. The Brooklyn Bridge is 1,866 feet long.