48" means 48 inches
anyway
the perimiter is the distance around or the sum of the sides
perimiter=48=x+3+4x-1+2x-3=7x-1
48=7x-1
add 1 to both sides
49=7x
divide both sides by 7
7=x
x+3=7+3=10
4x-1=4(7)-1=28-1=27
2x-3=2(7)-3=14-3=11
the sides are 10", 27" and 11"
x=7