In this study, I examined how 34 Spanish-speaking English language learners (ELLs) used their linguistic resources (English and Spanish) and language modes (oral and written language) to demonstrate their knowledge of proportional reasoning in a dual language mathematics assessment task. The assessment allows students to see the item in both English and Spanish, to listen to someone read aloud the item in English or Spanish, to provide oral or written responses in English, Spanish, or both for selected constructed-response items. The assessment was piloted in three algebra classrooms at a middle school and a high school in the United States. Data included students' responses, the amount of time it took students to complete each item, the language that the students used in each item, the language mode they used to complete the constructed-response items, the number of times the students listened to the read alouds, and responses to a short survey. This study reports on how Spanish-speaking ELLs performed on the assessment task, the linguistic resources and the language modes they used to access and to respond to the task, and how language and mode use impacted performance and the time spend on the test items.