At first, she had +2y in the upper and -5y in the lower.
She multiplied the upper by 5 . Then she had +10y in the upper.
She should multiply the lower by 2 . Then she'll have -10y
there. She'll be able to add the two equations, and the 'y's will
go away. She'll be left with a single equation with only 'x' in it,
and she can solve that one for the value of 'x'.
