For what value of the constant $a$ does the system of equations below have infinitely many solutions? \begin{align*} 2x + 5y &= -8,\\ 6x &= 16 + a - 15y \end{align*}
+36915 2x + 5y = -8
6x + 15y = a Multiply top equation by 3 to get:
6x + 15y = -24 if a and -24 are equal the two equations are the same and there are infinite solutions
a = -24
