For a certain value of k, the system
3a + 4b = 7,
6a + 4b = k - 3a - 8b
has infinitely many solutions (a,b). What is k?
Simplify the second equation as
9a + 12b = k
Notice that the left side is just 3 ( 3a + 4b)
So.....to provide infinite solutions, the equations must be the same which means that 3* 7 = k = 21
