Solve the system using substitution and describe your steps.
x=y-3
2x+y=12

6(2x+y)+2(x+4y) how can i solve this

If 1/√5+1/√5+1=p+q√r , find the values of p, q and r

Ascientist has 50 grams of a radioactive element. the amount of radioactive element remaining after t days can be determined using the equation (1) after two days the scientist receives a second shipment of 50 grams of the same element. the equation used to represent the amount of shipment 2 remaining after t days is 10) - 50 which of the following is an equivalent form of the expression for the amount remaining in shipment 2? what’s the answer?