X+2y=19 and x+y=13 in substitution methood​

If you roll two fair dice (one black die and one white die), in how many ways can you obtain a 4 on at least one die?

If the measure of xyz is 81 what is the measure of yz

Find the slope and the y-intercept if there's one and the equation of the line given these two points( 3, 2) and( 3, -4)