it is given in the question that
Alpha printing will make 400 brochures for $100. Omega printing will make 1,000 brochures for $100.
For Alpha, cost of 1 brochure is
[tex] = \frac{100}{400} = $0.25 [/tex]
For Omega,
Cost of 1 brochure is
[tex] = \frac{100}{1000} = 0.10 [/tex]
So choosing Omega printing, you will save
[tex] = 0.25-0.10 = $0.15 [/tex]
on each brochure .