Find the value of each variable I need 6-10

Answer:
6) 9x-25+9x-25(sum of base angles)
9x-25+9x-25+104=180(sum of angles in a triangle)
collect like terms
9x+9x-25-25+104=180
18x-50+104=180
18x+54=180
18x=180-54
18x=126
divide both sides by 18
18x÷18=126÷18
x=7