Answer:
60 degrees
Step-by-step explanation:
First of all, we have to set up an equation to solve this. The angles of a triangle add up to 180 degrees. We need to find the internal angle of C, which would be 180-(10x-45).
For our equation, we can set 3x+4x+[180-(10x-45)] equal to 180.
Add like terms:
7x+[180-(10x-45)] = 180
Distribute:
7x+180-10x+45 = 180
Add like terms once again:
-3x+225 = 180
Subtract 225 on both sides:
-3x = -45
Divide by -3 on both sides:
x = 15
Plug in 15 for x in the value 4x:
<B = 60 degrees
