How can you tell when an equation in one variable has infinitely many solutions or no solutions

What is x and y intercepts for y=x+7

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?

What is the name of a polygon that has four congruent sides and theses angle measures 60,120,60,120?