Hey there!
7x + 1 + 50 + 80 = 180°
COMBINE the LIKE TERMS
7x + 51 + 80 = 180°
7x + 131 = 180°
SUBTRACT 131 to BOTH SIDES
7x + 131 - 131 = 180° - 131
CANCEL out: 131 - 131 because it gives you 0
KEEP: 180 - 131 because it help solve for the x-value
NEW EQUATIONS 7x = 180 - 131
SIMPLIFY IT!
7x = 49
DIVIDE 7 to BOTH SIDES
7x/7 = 49/7
CANCEL out: 7/7 because it gives you 1
KEEP: 49/7 because it gives you the x-value
NEW EQUATION: x = 49/7
SIMPLIFY IT!
x = 7
Therefore, your answer is: x = 7
Good luck on your assignment & enjoy your day!
~Amphitrite1040:)