Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$13+i$
Multiply each term of the first complex number by each term of the second, then combine like terms and use the fact that $i^2=-1$ to obtain: $$(5+3i)(2-i)=5(2-i)+3i(2-i) \\=10-5i+6i-3i^2 \\=10+i-3(-1) \\=10+i+3 \\=13+i$$