Assuming that b>0 and c>0:
log(a)=3×log(b)-2×log(c)=
log(b³)-log(c²)=
log(b³/c²)
Hence a=b³/c²
450
10*12= 120 the bottom of the box
10*7.5= 75 one side
75*2= 150 two sides
12*7.5= 90 another side
90*2= 180 two other sides
120+150+180 = 450
Hope this helped :)
Your answer will be y=-3x+4