Y $=10+3\mathrm{.}5$ x$1+5$ x$2+$ e is interpreted in the following way:

An increase in $1$ unit of x$1$ implies an an increase in $3\mathrm{.}5$ units of Y$.$

A decrease in $1$ unit of x$1$ implies an an increase in $3\mathrm{.}5$ units of Y$.$

An increase in $10$ units of Y implies an an increase in $3\mathrm{.}5$ units of x$1.$

An increase in $3\mathrm{.}5$ units of x$1$ implies an an increase in $1$ unit of Y$.$