Idont get question 19& 20 show the working out on paper .

arrange the equations with like terms in columns.

analyze the coefficients of x or y.

add the equations and solve for the remaining variable.

substitute the value into either equation and solve.

check the solution.

step-by-step explanation:

(3x-8) or (3x+8)

step-by-step explanation:

the function makes a strait line horizontally with no x intercept but a y intercept at 9.

6mm^3 or .6cm^3

      216

      /   \

  36     6

  /   \     /

6     6   6

factor trees are nice.