First we should work out what 40% is in decimal form.
We can do this by doing 40 divided by 100 which gives us: 0.40
Therefore 40% in decimal form is 0.40.
Next we do 80 x 0.40 which gives us 32, this means Justin has already made 32 illustrations.
Next we do 80 - 32 which gives us 48, this means Justin still has to do 48 illustrations.
I hope this helps!