Rooney's company decides to buy some keyboards, mouse cursors and PC Cameras. They have a budget for $1500 to spend on $30 keyboards, $20 mice and $50 cameras. Additionally, the number of the cursors should be equal to that of the keyboards and the keyboards are twice the numbers of cameras. How many of each item should he buy? The only thing I'm struggling with is turning the word problem into linear system of equations. Can someone help me out?​