Answer
The right expression of provided algebraic expression is \[15x+21\].
Work Step by Step
Distributive property:
\[c\left( a+b \right)=ac+bc\]
Standard form of distributive property is:
\[c\left( a+b \right)=ac+bc\]
Now use the distributive property for the provided expression is:
\[3\left( 5x+7 \right)=15x+21\]
Being a teacher of a student, I would suggest him to learn a standard form of distributive property so that, next time he wouldn’t repeat that error.
