## Algebra 1: Common Core (15th Edition)

From the problem, we know Luis raised 21 dollars, earning 1.75 dollars for every mile (x) he ran: $1.75\times x=21$ We can now isolate $x$ by dividing both sides of the equation by $1.75$: $(1.75\times x)/1.75=21/1.75$ $x=12$