If the genotype of a hybrid F₁ is  RrYy, what is the probability of formation of a gamete Ry given both genes are located on two different chromosomes. 

The probability of formation of gamete Ry from the plant having genotype RrYy, when both  the genes are located on different chromosomes, there is equal chance of inheritance of  all genes.

Rr can form gametes R and r. So, the probability of R allele in a gamete is 1/2

Yy can form gametes Y and y. So, the probability of y allele in a gamete is 1/2.

By multiplying the individual frequencies, the probability for gamete with gene combination Ry = 1/2 x 1/2  = 1/4