3a+5b-9: a=2, b=3 that is my question I need help

If you are trying to move an attached term across the equal sign (=), what operation would you use to move it?

Astock has a 25% probability of increasing by $10 and a 75% probability of decreasing by $5. what is the stocks expected increase or decrease?

Tobias gold sells computers at the office center he's guaranteed a minimum salary of $1,959 per month plus 6.3% commission on total sales how much in total sales is he