Answer:

Step-by-step explanation:
For each right-angled triangle:

Because 
we have an equation

multiplying both sides by x, we get 
dividing both sides by 0.4 and 
using calculator, we divide 12 by 0.4
and finally x=30
Do you mean like this?
Y = -x - 4
Y = x
x = -x - 4
2x = -4
x = -2
Therefore y = -2
1200 ... i think this you mean
∠ACB is an inscribed angle, so
m∠ACB= (1/2)mAB =(1/2)*50=25⁰
m∠ACB= 25⁰