Can anybody help with this algebra formula question? ☺

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heres a description of what needs to be done: evaluate the following formulas. use the given values to find the values of the remaining variables.
a=x+y+z/3 a=6 x=9 y=2 find z

z=?

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a = (x+y+z)/3
3a = x+y+z
3*6 = 9+2+z
z = 18-11
z = 7

6=9+2+z/3.... add 9 and 2 together
6=11+z/3 ..... subtract 11 from both sides (11 minus 11 cancels out, and 6 minus 11)
-5=z/3 .......... multiply 3 to all sides (3 times 3, and -5 times 3)
z=-15 .......... your answer

Check
substitute z for your answer (-15) when you check
6=9+2-15/3........divide first (-15/3)
6=9+2-5............now add (9+2)
6=11-5..............now subtract (11-5)
6=6..................your answer is correct

Z=-15

Substitute variables with its values:

6=9 + 2 + z/3

6 -9 -2 = 9 -9 + 2 -2 + z/3

-5 = z/3 5 * 3 = (z/3)*3

-15 = z

check

6 = 9 + 2 + (-15/3)

6 = 9 + 2 - 5

6 = 6

z=7 if a=(x+y+z)/3