what happens if 2 acids are mixed

Dear student!

Two acids or two bases mixed together will have no reaction and will be the acid or base only.

However, when a weak acid is mixed with a strong acid then the weak acid acts like alkaline and the pH of the resulting solution will be slightly lower than the weak acid (as lower pH means higher acidity) and slightly higher than the strong acid, means the pH of resulting solution will be between the range of pH of strong acid and weak acid.