I wrote this 20-question circuit as a request for colleague Kelsey Russell who teaches 8th grade math. She texted me, "I'd really love a circuit on distributing and combining like terms with some fractions in it too." I included 4 word problems and even a problem which has some decimals. Progressive in nature, the circuit starts with 2(3x - 7) and proceed from there. There are no squares (i.e. no situations where students will multiply and get a result x^2). None of the questions require the use of a calculator, but you might have your students use one to speed them up.
I do not include an answer key since the answers are imbedded in the circuit; it is how students move from one question to the next. This element of self-check is essential because it requires students to ask questions if they can not find their answer. The only thing the teacher needs to do is work the circuit ahead of the students to decide what, if any, vocabulary / notation / concepts should be addressed before the students begin. You will love the sounds of your students as they work through a circuit!
If you suspect an error or get stuck, please do not hesitate to email me at firstname.lastname@example.org.