Answer:
75% red, 25% other color (brown?)
Step-by-step explanation:
A cross between two heterozygous red eye flies (Rr x Rr)
R r
R RR Rr
r Rr rr
The possible genotypes are RR, Rr, and rr. There are two possibilities of Rr.
Since the heterozygotes have red eyes, the red eye allele must be dominant. Therefore, RR and Rr genotypes will all have red eyes. That means 3/4 (75%) of offspring will have red eyes. 1/4 25% are h0m0zygous recessive (rr), and will therefore have the other eye color (question doesn't mention which colour this is, it is likely brown)