The equation of a line is based on two simple questions: "How much #y# changes when you add #1# to #x#?" and "How much is #y# when #x=0#?"
First, it's important to know that a linear equation has a general formula defined by #y = m*x + n#.
Having those questions in mind, we can find the slope (#m#) of the line, that is how much #y# changes when you add #1# to #x#:
#m = (D_y)/(D_x)#, with #D_x# being the difference in #x# and #D_y# being the difference in #y#.
#D_x = 0-(25) = 0 - 25 = -25#
#D_y = 2-(-10) = 2+10 = 12#
#m = -12/25#
Now, we need to find #y_0#, that is the value of #y# when #x=0#. Since we have the point #(0,2)#, we know #n = y_0 = 2#.
We now have the slope and the #y_0# (or #n#) value, we apply in the main formula of a linear equation:
#y = m*x + n = -12/25 * x + 2#
