#### Answer

$28x^8$

#### Work Step by Step

We start with the given expression: $(4x^5)(7x^3)$
We rearrange and regroup the factors by like terms: $(4\times7)(x^5x^3)$
We multiply the constants: $28x^5x^3$
To multiply powers with the same base, we add the exponents: $28x^{5+3}=28x^8$