How do you simplify 5x^2*x^4 and write it using only positive exponents?

$5 {x}^{6}$
We know for the rules of indices that ${x}^{m} \times {x}^{n} = {x}^{m + n}$
Therefore: $5 {x}^{2} \times {x}^{4} = 5 \times {x}^{2 + 4} = 5 {x}^{6}$