the pH of a solution is 10 and other is 12 when equal volumes of these low are mixed the pH of the resulting solution is?

Answer 1

"equal volumes of these low" WHAT?

If the acids are strong acids we can take 100 mL of each.
For pH = 10 we have 100 x 1E-10 = 1E-8 millimols.
Add 100 mL pH = 12 and we have 100 x 1E-10 millimols.
Add 1E-8 mmols and 1E-10 mmols = 1.01E-8 millimols and that is in 200 mL so
(H^+) = 1E-8 mmols/200 mL = 5.05E-11 and pH = ?. About 10.3
You can use 50 mL each or 1000 mL each ( or any equal numbers) and the answer will be the same.