to get the equation of any line you need two things: the slope of the line and any point passes by the line
here we have two points passes by the line ( 0,2) (4,0) by knowing those two points we can get the slope easily as follow
slope (m) = (0-2) / (4-0) so m = -1/2 now we have the slope and point (0,2) the general equation of the line is y = mx +c where m is the slope and c is a constant. so the equation will be y = -1/2 x + c and to get the value of the constant, sub by the point (0,2) in the pervious equation
that will be 2 = -1/2 (0) + c then c = 2
now the final equation of the line will be y = -1/2 x + 2 to make the equation look better, multiply it by 2 and move x to the left-hand side 2y + x = 4
