How do I fill this out? Im not sure how to?

z=-21

Step-by-step explanation: (9-3)/2=(6+z)/5

We move all terms to the left:

(9-3)/2-((6+z)/5)=0

We add all the numbers together, and all the variables

-((z+6)/5)+6/2=0

We add all the numbers together, and all the variables

-((z+6)/5)+3=0

We multiply all the terms by the denominator

-((z+6)+3*5)=0

We calculate terms in parentheses: -((z+6)+3*5), so:

(z+6)+3*5

We add all the numbers together, and all the variables

(z+6)+15

We get rid of parentheses

z+6+15

We add all the numbers together, and all the variables

z+21

Back to the equation:

-(z+21)

We get rid of parentheses

-z-21=0

We add all the numbers together, and all the variables

-1z-21=0

We move all terms containing z to the left, all other terms to the right

-z=21

z=21/-1

z=-21

the answer to this question is "motor unit"