Evaluating Expressions

5m – 6 when m=7

6m – 3k

when m=7 and k=2

c + (a² + b) – 15

when a=5 , b= 3 and c=4

 $\frac{\left(y-x\right)+x}{x}$   
when x=5 and y=8

5x + 2x - y

when x=5 and y=8

xy – z²

^{when x=6 , y=12 and z=4}

 $\frac{2x+y}{z}$  
when x= 6,y=12, and z=4

 $\frac{kn}{n}$  
when k=2 and n=4

 $5b^3$  
when b=

3(9f+5c)

when f=8 and c=5