how do you prove a inverse square relationship with this specific data. (not talking abt inverse square law)

geno- 25%BB 50%Bb 25%bb

Pheno: black, kermode(white)

Explanation: the top of the punnett square should have Bb and the side should have Bb.

Square one should be BB square two should be Bb square three should be Bb and square 4 should be bb * note* the percentages should add up to 100 and use percentages of 25