Answer:
t = 18, u = 123
Step-by-step explanation:
The external angle of a triangle is equal to the sum of the 2 opposite interior angles.
7t - 23 is an exterior angle of the triangle, thus
7t - 23 = 49 + 3t ( subtract 3t from both sides )
4t - 23 = 49 ( add 23 to both sides )
4t = 72 ( divide both sides by 4 )
t = 18
----------
7t - 23 and u - 46 are adjacent angles and supplementary, thus
7t - 23 + u - 46 = 180 ← substitute t = 18
7(18) + u - 69 = 180
126 + u - 69 = 180
57 + u = 180 ( subtract 57 from both sides )
u = 123
----------------
