Fractions make an otherwise easy one-variable equation feel slow and error-prone. The SAT knows this and writes equations with denominators on purpose. The fix is a single move at the start: multiply every term on both sides by the least common denominator so no fraction survives past line one.
Start with x over 3 plus x over 4 equals 14. The denominators are 3 and 4, so the least common denominator is 12. Multiply every term by 12. The first term becomes 4x, the second becomes 3x, and the right side becomes 168. Now the equation is 7x equals 168, so x equals 24. No fraction arithmetic happened at any point.
The word every is doing real work in that instruction. Students multiply the fraction terms and forget the whole-number term, which quietly changes the equation. In the example above, skipping the 14 would leave 7x equals 14 and an answer of 2, which is wrong by a factor of 12. Write the multiplier in front of each term before you simplify any of them.
When a whole expression sits over a denominator, keep it in parentheses. In the equation the quantity 2x minus 5 all over 4 equals 3, multiplying both sides by 4 gives 2x minus 5 equals 12, so 2x equals 17 and x equals 8.5. If instead the equation were the quantity 2x minus 5 all over 4 plus x over 2 equals 3, the least common denominator is 4, giving 2x minus 5 plus 2x equals 12, so 4x equals 17.
Decimals are the same problem wearing different clothes. An equation like 0.4x plus 1.2 equals 3.6 becomes far easier if you multiply every term by 10, giving 4x plus 12 equals 36 and x equals 6. Multiply by 10 for one decimal place, by 100 for two. The SAT calculator can handle decimals directly, but clearing them still reduces the number of keystrokes where a mistake can enter.
One caution: clearing denominators is legal only because you are multiplying both sides by the same nonzero number. If the variable itself appears in a denominator, you are dealing with a rational equation rather than a linear one, and any solution that makes a denominator zero has to be thrown out at the end.