If the angles are supplementary angles, that means that they add up to be 180˚.
Angle A is 3x+17 (17 more than 3 times a number) and Angle B is 7x+3 (3 more than 7 times the number).
Both of these added together is equal to 180, so you get: 3x+17+7x+3=180
Combine like terms and get: 10x+20=180
Subtract 20 from both sides: 10x=160
Divide both sides by 10: x=16
Now you have your number.
To find the angles, plug the number back into the statements.
Angle A: 3(16)+17=65˚
Angle B: 7(16)+3=115˚
Check to make sure they add up to equal 180: 65+115=180 √
And you're done!
