Answer:
for the first photo the answer is 5x + 6(-x + 4) = 13
Step-by-step explanation:
if y equals to -x +4
then replace the y in this equation: 5x + 6y = 13 with this ( -x +4 ) its simple.
I cannot answer the other 2 photos at the moment but ill see if I can whenever else I have time.
z=24 y=5 x=12
x+8=20 x=20-8 x=12
z+1=25 z=25-1 z=24
y+10=15 y=15-10 y=5
