Which correct postulate, theorem, property, or definition that justifies each of the following statements. Answers are in picture

Thanks in advance :D

The equation y=mx+b is the slope-intercept form of the equation of a line. what is the equation solved for b? y-m=b y-mx=b y/mx=b y/m-x=b

What is the solution to this system of equations? y= 2x - 3.5 x - 2y = -14

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z