Your answer is 4,
You take r which is 10 and plug it in the equation, which is 3(10)=10+5s.
Multiply, 30=10+5s.
Now we cross over our like terms, 10 to 30. (TIP; if a number crosses the equal sign it changes signs).
So, now we subtract; 30-10=5s
Which gives us 20=5s.
All that's left is to divide 20 by 5.
20/5 = 4
