19-21. any help is appreciated

Ageologist had two rocks on a scale that weighed 4.6 kilograms together.rock a was 0.5 of the total weight.how much did rock a weigh?

Which expression shows the sum of the polynomials with like terms grouped together

Let hh represent the number of hummingbirds and ss represent the number of sunbirds that must pollinate the colony so it can survive until next year. 6h+4s > 746h+4s> 74 this year, 88 hummingbirds pollinated the colony. what is the least number of sunbirds that must pollinate the colony to ensure that it will survive until next year?