What digits can be in the ones place of a number that has five as the factor

The equation x2 – 1x – 90 = 0 has solutions {a, b}. what is a + b?

Afamily has five members. a mom, a dad, two sisters, & a brother. the family lines up single file. what is the probabillity that the mom is at the front of the line

If sin(x) = 0 and cos(x) = 1, what is tan(x)?