in multiplying numbers/variables having the same base involving exponents this exponential law will apply:
[tex]a^m(a^n) = a^{m+n}[/tex]
since the base x is common then you will have it as:
[tex]x^{10}(x^{12}) = x^{10+12}[/tex]
[tex]x^{10+12} = x^{22}[/tex]
