Answer:
155°
Step-by-step explanation:
The sum four angles is 360° so:
60°+45°+100°+x=360°
x = 360°-100°-45°-60°=155°
15x+100=28
x=-6/5
The answer is -6/5
One decimal place to the left decimal point is the place.
Let's say David's age right now is x years
x + 6 = 2(x - 7)
x + 6 = 2x - 14
x = 20
Therefor David is 20 years old
