Answer:
x = 21
Step-by-step explanation:
Diagonal angles are equal to eachother, so 143 = 6x +17
143 = 6x + 17
Subtract 17 from both sides
126 = 6x
Divide by 6
21 = x
To check put x as 21
143 = 6(21) + 17
Mutiply 6 by 21
143 = 126 + 17
add 17
143 = 143
