lets call each corner (the bracket points) as A, B, and C in that order.
So, for the side AB we notice that we are moving the the right by 3 units so tbe length is 3
For the side AC, we can use python theorm and say our opposite side is the rise which is 1 and the adjacent is 4. so 4²+1²= c² . this gives sqrt( 17) which is the also the length of the side.
For BC, its the same method but now our chnage is 2²+4²=c² , which leaves us with sqrt(20). And that is your final Length.