How to do it geometry

Answer:
Hey Im not sure I understand the question but I think the answer is
x=15
Step-by-step explanation:
5x+ 3x+ 4x= 180,( I made it equal to 180 because that is the measure of angles for triangles)
add the x
12x= 180
divide
180/12
x=15
(EXTRA)
To prove it you can plug 15 into any of the x's to add it up and it will equal 180
Answer:
x = 15 and
the 3 angles are 45, 60 and 75 degrees.
Step-by-step explanation:
The 3 angles of any triangle add up to 180 degrees, so:
3x + 4x + 5x = 180
12x = 180
x = 15.
Angles:
3*15 = 45
4*15 = 60
and
5*15 = 75.