Hello Ngoc,
The best part about this word problem is that the words can guide you!
"If the sum of eight and a number is multiplied by five, the result is forty-five. What is the number?
Sum = addition
"a number" in this case is a variable - let's call it "a"
"is multiplied" = in this case indicates sum of the first part multiplied by
result means equals "="
Let's break it down:
"If the sum of 8 and a number..." = 8 + a
"...is multiplied by 5..." = (8 + a) x 5
"the result is forty-five." (8 + a) x 5 = 45 There's your equation!
You want to divide by 5 on both sides, leaving 8 + a on the left and 45/5 (I'll let you get the answer yourself). Subtract 8 from that answer and you'll find "what is the number"!
I hope this helps. If you need any additional help, please don't hesitate to reach out. I can tutor through video conference too! Good luck!
