If x + 4y = 18 and x − 4y = 2, then x = ?

x + 4y = 18 and x − 4y = 2

I would use substitution

add the 2 equations together

  x + 4y = 18

+ x − 4y = 2

2x + 0y = 20

2x = 20

divide each side by 2

2x/2 = 20/2

x = 10

x=1

f(x) = - 2/3x + 5; f(5/2)

substitute 5/2 in for x:

f(5/2) = -2/3(5/2) + 5

simplify the right side:

f(5/2) = -5/3 + 5

f(5/2) = 10/3

answer:

f(5/2) = 10/3

i hope this you!