Question 1049483
the {{{equations }}} are


{{{A+B}}}={{{90}}} eq 1
{{{B+C}}}={{{90}}} eq 2

{{{3x+y+x+4y+2}}}={{{90}}} eq 1
{{{x+4y+2+3y-3}}}={{{90}}} eq 2

{{{4x+5y}}}={{{88}}} eq 1

{{{x+7y}}}={{{91}}} eq 2

*[invoke linear_substitution "x", "y", 4, 5, 88, 1, 7, 91 ]