34 points -2[3x-(b+2x)+(x-3b)] plz show steps i'm stuck

What's the difference between: x≥0 and nonnegative integer. ?

Is δ pmr similar to δ smn ? if so, which postulate or theorem proves these two triangles are similar?

Astandard deck of cards contains 52 cards. one card is selected from the deck. (a) compute the probability of randomly selecting a seven or king. (b) compute the probability of randomly selecting a seven or king or jack. (c) compute the probability of randomly selecting a queen or spade.