While helping her grandparents clean out their attic, Mara found her grandfather's old baseball card collection. 40% of his cards were from the 1950s. If 30 cards were from the 1950s, how many baseball cards did Mara's grandfather have in all? Please give only an
answer.

The expression 20l+25g-10 calculates the number of dollars that the abc lawn company. how many dollars does the company make from raking 444 gardens and mowing 333 lawns

The physical fitness of an athlete is often measured by how much oxygen the athlete takes in (which is recorded in milliliters per kilogram, ml/kg). the mean maximum oxygen uptake for elite athletes has been found to be 60 with a standard deviation of 7.2. assume that the distribution is approximately normal.

How to solve a simultaneous equation involved with fractions?