MathPencil lessons
Step-by-step solver
Two boards. The first solves an equation with one letter in it. The second puts a value in place of the letter and works the expression out. Both print the working line by line, which is the part a teacher marks.
Solve an equation
One letter, one answer, and every step it took to get there.
Evaluate an expression
Give the letter a value, and see the substitution before the answer.
Why the answers are fractions
A third written as a decimal is 0.333333333333, and that is already wrong by the time the screen runs out of room. The solver carries the numerator and the denominator as whole numbers the whole way through and divides only when the division comes out exact, so a third stays 1/3.
That is also how you are expected to write it. An answer of 7/2 is marked correct where 3.5 may not be, depending on what the question asked for.
What it solves, and what it turns down
It handles one unknown, appearing as a plain letter, with the four operations and brackets around them. That covers one-step equations like x + 8 = 15, two-step equations like 2x + 5 = 17, and equations with the letter on both sides.
Anything past one letter is turned down with a sentence saying which rule it broke. A letter squared, a letter on the bottom of a fraction, or two different letters are all algebra rather than pre-algebra, and a tool that answered them here would be teaching a method the course has not reached.
It is built for checking work rather than replacing it. The steps are the output; the answer on its own is the least useful part of what it prints.
For everything else
For roots, powers and trigonometry there is the scientific calculator, which applies the order of operations. For a running total that prints to a tape, the adding machine. To learn the method rather than check it, the chapter on expressions, variables and equations is where the balance rule is explained, and the course contents lists the rest.