I'm assuming you want us to solve for the unknown variable z

Combine like terms on the right side

Use the distributive property on the left side

Add both sides by 20 to cancel out the "-20" on the left side

Divide both sides by 10

That is the value of the known variable, z, in this equation. Let me know if you need any clarifications, thanks!
~ Padoru
Divide 28.26 by 3.14
The answer is 9