Modeling the above problem in matrix form we have,
[3 5;9 7]*[x y]'=[49 77]'
AX=b
X=inv(A)*b
X=[1.7500 8.7500]'
ie x=1.7500 and y=8.7500
It's asking you to set -x and x equal to each other...
-x = x
2x = 0
x = 0.
0.75
to find the decimal of a fraction divide the top number by the bottom number so 3 divided by for; aka the numerator by the denominator
the other missing angle is 60