Answer:
m<ABC=40
Step-by-step explanation:
Ok so we need to break up this problem.
m<ABC=4x
m<BCA=7x-20
m<A= 90 degrees (We are given a right angle here)
Because of the Triangle Sun Theorem, all the angles here would add up to 180 degrees. So..
4x+7x-20+90=180
Solve
x=10
Then we look back and see that m<ABC is 4x
We plug in x
4(10)=m<ABC
m<ABC=40
