Question 310925
{{{35x + 21y = -77}}}
{{{35x - 10y = 65 }}}
You're good up to here but you need to subtract the equations instead of add. 
If you add 35x and 35x you get 70x and not 0. 
Or just change the sign of eq. 2 and add.
{{{35x + 21y = -77}}}
{{{-35x + 10y = -65}}}