表达式2: StartFraction, 20 Over StartAbsoluteValue, "x" , EndAbsoluteValue , EndFraction minus StartFraction, 5 Over StartAbsoluteValue, 8 minus "x" , EndAbsoluteValue , EndFraction20x−58−x
2
表达式3: StartFraction, 20 Over StartAbsoluteValue, "x" , EndAbsoluteValue , EndFraction20x