math
posted by Mage on .
the system of linear equations below has a unique solution for all but one value of a :
5 x  5 y = 25
48 x + a y = 240
What is this exceptional value for a ?

If the two lines would be parallel, we could not find a solution,
that happens when
5/48 = 5/a
5a = 5(48)
a = 48