Answer:
1. x = 65
2. x = 40
3. x = -7
4. x = -4
5. x = -7
6. x = 4
Step-by-step explanation:
Angles in a triangle always add up to 180 degrees.
Thus, for each triangle you can write an equation setting the sum of the three angles equal to 180, and solving for x.
1. 180 = 80 + 35 + x
180 - (80 + 35) = x
180 - 115 = x
65 = x
2. 180 = 70 + 70 + x
180 - (70 + 70) = x
180 - 140 = x
40 = x
3. 180 = 76 + 41 + (x+ 70)
180 - (76 + 41) = x + 70
180 - 117 = x + 70
63 = x + 70
63 - 70 = x
-7 = x
4. (the red square means its a right angle = 90 degrees)
180 = 90 + 25 + (x + 69)
180 - (90 + 25) = x + 69
180 - 115 = x + 69
65 = x + 69
65 - 69 = x
x = -4
5. 180 = 50 + (57 +x) + (x + 87)
180 - 50 = (57 +x) + (x + 87)
130 = (57 +x) + (x + 87)
combine like terms
130 = 144 + 2x
130 - 144 = 2x
-14 = 2x
-7 = x
6. 180 = 80 + (9x + 4) + (16x - 4)
180 - 80 = (9x + 4) + (16x - 4)
100 = (9x + 4) + (16x - 4)
combine like terms
100 = 25x + 0
100 = 25x
4 = x
