- Pick the unknown. Click O, M or F: whichever the question asks you to find becomes x.
- Enter the multiplier as a decimal. Power it up for repeated changes; add a second one for changes in a row.
- Move pieces diagonally across the equals sign (Bishop) until x stands alone. Click a power on x to undo it.
- CALC does the arithmetic. When x is a multiplier, read it back as a percentage yourself. CALC, Flip and reading are free; slips are wrong choices.