A math test has 30 problems. Some problems are worth 2 points and some problems are worth 3 points. The test is worth 80 points total. Which system can be used to determine the number of 2-point problems and the number of 3-point problems on the test?

Johnny rode his bike to a friends house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was unable to play. what was his displacement for the total bike ride trip? what could you use as a reference point ? show the steps to solve this problem.