PLEASE HELP!! EXPLANATION TOO PLEASE THANK YOU
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x=57

Step-by-step explanation:

a triangle has a sum of 180 degrees

that angle 51 is vertical to the angle across it so it is 51

we do math now

180-72-51=57

I hope this helped :))

b.an increase in a causes b to decrease

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18