Step-by-step explanation: Once you subtract from both sides, in order to solve for y (as the equation needs to be in the slope-intercept form, otherwise known as ), you end up with , which is the right answer. It is the correct answer because the y-intecept shown in the equation matches what is on the graph, in addition to the fact that the slope is just .
Three main methods come to mind: Substitution method, Elimination method, Matrix row-reduction.The first two methods are taught in early grades in most high schools. Matrix row-reduction is taught in senior years in high school, or more likely, in the early years of a university math or science program.