For what ordered pair $(a,b)$ are there infinite solutions $(x,y)$ to the system\begin{align*} 3ax+3y&=5b,\\ 2x+y&=5. \end{align*}
3ax + 3y = 5b
2x + y = 5 multiply through by 3 → 6x + 3y = 15
To have infinite solutions the equations must be the same ......this implies that
3a = 6 and 5b = 15
a = 2 b = 3