Can anybody answer this for me?

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

Ajar of gumballs contains 4 reds, 2 greens, and 6 blues. what is the probability of getting two blues in a row without replacement?

Anna is constructing a line segment that is congruent to another segment ab. for the construction, which tool should be used to mesure segment ab