its d, I just solved it...
You would subtract the tax first which 62.99-2.99=60$. Then you would divide the $60 left by 6 and 60 divided by 6 equals 10 so each shirt costs $10.
Isn't it 1/8?
I hope this helped i think i just simplified xD
(a) * (a+1) = 420
a^2 + a = 420
a^2 + a - 420 = 0
(a+21)(a-20) = 0
a = -21 OR 20
The two integers can be -21 and -20, OR 20 and 21.