In drosophila, red eyes is the wild-type phenotype. Several different genes (with each gene existing in two or more alleles) are known to affect eye color. One allele causes purple eyes, and a different allele causes sepia eyes. Both of these alleles are recessive to red eye color. When flies with purple eyes were crossed to flies with sepia eyes, all the F_1 offspring had red eyes. When the F_1 offspring were allowed to mate with each other, the following data were obtained: 146 purple eyes
151 sepia eyes
50 purplish sepia eyes
444 red eyes
Explain the pattern of inheritance.

9:3:3:1.

Explanation:

The offspring produced with the ratio of 9:3:3:1 in this crossing. In the F1 generation, all the organisms have the dominant allele but when the two F1 organisms are allowed to mate with each other, the highest ratio of offspring i. e. 9 having dominant allele is produced, hybrid organisms are also produced in the ratio 3 and in the last the offspring that have recessive allele is produced having the ratio of 1.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)