Can you recommend academic subject tutoring sites for reviewing difficult math and science topics?

Yes — here are some solid academic tutoring sites for math and science review, depending on what kind of help you want:

Live tutoring / homework help

• Khan Academy — Free lessons and practice for math, physics, chemistry, biology, and more. Great for reviewing fundamentals and filling gaps.
• Chegg Study — Paid service with step-by-step solutions and tutoring help for many math/science courses.
• Wyzant — Lets you find and book one-on-one tutors in specific subjects, including advanced math and sciences.
• Varsity Tutors — Offers live online tutoring, test prep, and small-group classes.
• Tutor.com — On-demand tutoring, often available through schools, libraries, or subscriptions.

Free learning and review

• Khan Academy — Best free option for structured review.
• CK-12 — Free digital textbooks, videos, and practice in math and science.
• Paul’s Online Math Notes — Very helpful for calculus, algebra, and related math topics.
• OpenStax — Free college-level textbooks for math, chemistry, physics, biology, and more.

Science-specific support

• Physics Classroom — Excellent for high school physics concepts and problem-solving.
• Crash Course — Short video explanations for biology, chemistry, physics, and other subjects.
• BioInteractive — Strong for biology and life sciences.

If you want:

• Affordable practice and lessons: Khan Academy, CK-12, OpenStax
• Personalized tutoring: Wyzant, Varsity Tutors, Tutor.com
• Step-by-step problem help: Chegg Study

If you want, I can also give you a ranked list by price, best sites for high school vs. college, or sites for specific subjects like calculus, chemistry, or physics.