Please help, solve for x

What are “like terms”? why can we only add like terms?

Adriana sold 50 shares of a company’s stock through a broker. the price per share on that day was $22.98. the broker charged her a 0.75% commission. what was adriana’s real return after deducting the broker’s commission? a. $8.62 b. $229.80 c. $1,140.38 d. $1,149.00

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)