You and your friend skate at the same rate. You complete 8 laps in 13 minutes. How long does your friend take to complete 16 laps?

Ametalworker has a metal alloy that is 30? % copper and another alloy that is 55? % copper. how many kilograms of each alloy should the metalworker combine to create 90 kg of a 50? % copper? alloy?

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)

How do you solving the solution of each system using elimination?