Look at the picture.
Corresponding Angles are equal.
Alternate Angles are equal.
Consecutive Angles add up to 180°.
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3a and 45 are Consecutive Angles. Therefore
3a + 45 = 180 |subtract 45 from both sides
3a = 135 |divide both sides by 3
a = 45.
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(2c - 1) and 45 are Corresponding Angles. Therefore
2c - 1 = 45 |add 1 to both sides
2c = 46 |divide both sides by 2
c = 23.
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3a and (12b + 3) are Alternate Angles. Therefore
3(45) = 12b + 3
135 = 12b + 3 |subtract 3 from both sides
132 = 12b |divide both sides by 12
b = 11.
