#### Answer

infinitely many solutions
{(x,y)|4x+y=5}

#### Work Step by Step

4x+y=5
4x-4x+y=5-4x
y=5-4x
Plug this value for y into the other equation
12x+3y=15
12x+3(5-4x)=15
12x+15-12x=15
12x-12x+15=15
15=15
Since this is a true statement without variables, this system has infinitely many solutions. The solution set is represented by either of the equations for example, {(x,y)|4x+y=5}