Question 691102
Once again, two angles are supplements when they add up to 180.

This time we will have two equations.
Equation 1: {{{A + B = 180}}}
Equation 2: {{{A = 60 + 3B}}}
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Plug (60 + 3B) into equation 1 for A
Equation 1: {{{A + B = 180}}}
{{{(60 + 3B) + B = 180}}}
Combine like terms
{{{60 + 4B = 180}}}
Subtract 60 from both sides
{{{4B = 120}}}
Divide both sides by 4
{{{highlight(B = 30)}}}
Now plug 30 into equation 2 for B
Equation 2: {{{A = 60 + 3B}}}
{{{A = 60 + 3*(30)}}}
Simplify
{{{A = 60 + 90}}}
{{{highlight_green(A = 150)}}}