When this 'l'-shape is rotated about the origin (0,0) by 90° counter-clockwise, which one of these would it look like?

The "L"-shape would look like it fell backwards and was laying on the ground. The little leg of the L would be pointing up into the air. 

A 90 degree counter clockwise turn means that it rotates left around the origin. It turns one half of half a turn, or 90 degrees.

I'll do the first one for you. it isn't very hard at all.on number one, you have (50 × 3), which equals 150, and (3 × 3), which equals 9. after you establish that, you add 150 and 9 together. so, (150 + 9) equals 159.this means that 53 × 3 = 159.