Elementary school students with mathematics difficulties experience significantly more complications in word problem-solving and mathematical reasoning of multiplying fractions than their peers. This study was conducted in two segments. The purpose of was to develop a “fun fraction” website for these students and test its usability before conducting an intervention. Altogether 53 college students and educational experts participated in the usability testing, rating the website’s instructional and interactive design features higher than its interface design. The purpose of was to investigate the intervention effect of explicit and systematic instruction with the virtual representational-abstract instructional sequence on two students with mathematics difficulties in upper elementary school grades. Although their word problem-solving accuracy and mathematical reasoning of multiplying fractions significantly improved (p < .05), their improvement score in word problem-solving accuracy was higher than mathematical reasoning. As a result of implementing a multiple-probe design across participants, Minjae displayed a significant intervention effect when using virtual manipulatives via an iPad, computer, or mobile device (p < .05), but Hyunwoo demonstrated significant effects only when using a computer or mobile device. Results of evaluation questions revealed that both experienced more difficulty in solving representative problems than arithmetic problems. Both students preferred using computers and iPads to mobile devices. This paper also discussed limitations, recommendations for future research, and educational implications.