Question 534615
{{{9x + y = 63}}}
{{{y = highlight(63-9x)}}}
.
{{{11x + 10y = 77}}}
{{{11x + 10 (highlight(63-9x)) = 77}}}
{{{11x + 630-90x = 77}}}
{{{630-79x = 77}}}
{{{553= 79x}}}
{{{7=x}}}