Answer
$7x^2+38xy+15y^2$
Work Step by Step
$$(x+5y)(7x+3y)$$
To multiply two binomials (expressions with two terms) multiply each term in the first binomial by each term in the second binomial:
$$=(x\times 7x)+(x\times 3y)+(5y\times 7x)+(5y\times 3y)$$ $$=7x^2+3xy+35xy+15y^2$$
Combine like terms:
$$=7x^2+38xy+15y^2$$
