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Please if you could help me!!!!
In tomatoes, tall vines (T) is dominant to dwarf vines (t), and round fruit (R) is dominant to oval fruit (r).  These two genes are linked with 15.2 cM between them.  You're given a tomato plant that is tall with round fruit, and you testcross it to produce the following collection of offspring:

88 tall plants that have oval fruit
82 dwarf plants that have round fruit
17 tall plants having round fruit
13 dwarf plants having oval fruit

Now you've decided to allow your tall, round fruit plant to self-fertilize.  If you count 500 self-cross offspring, how many would be expected to be dwarf plants that have oval fruit?

Much of the information here is to mislead. You do need to understand that a testcross is always with a double homozygous recessive i.e. ttrr. This plant is purebreeding so provides a chromosome that has both t and r on it.

This means that the genotype of the Tall, round plants is TtRr with T/R on one chromosome and t/r on the other chromosome.

When the TtRr plant undergoes meiosis it can produce haploid gametes TR, Tr, tR, tr but not in equal quantities (25%:25%:25%:25%) because the loci are linked. You are given the map distance of 15.2cM which indicates the recombination frequency 15.2%. This means that 84.8% of the time there will be no recombination and the gametes will be TR and tr but 15.2% of the time there will be recombination and the gametes will be Tr and tR. This means that the ratio of gametes produced will be TR:Tr:tR:tr = 84.8:15.2:15.2:84.8 and the percentage of gametes with these genotypes will be 42.4%:7.6%:7.6%:42.4%.

Dwarf plants with oval fruit have the genotype ttrr which happens when two tr gametes get together. This will happen 42.4%x42.4% of the time = 17.9776 (round to 18%). Note that this is very different to the independent assortment situation where tr would be produced 25% of the time and ttrr would be 25%x25% = 6.25% of the time.

Now if you count 500 offspring from this self-fertilisation then you should expect 18% of them to have the dwarf, oval phenotype = 90