Also, it should be noted that the ti-84 is a brick and will withstand the test of time. They’re no strangers to being dropped, scratched, and chucked at walls :))
@boneh3ad We’re both saying the same thing, perhaps the way I worded it was confusing. Work in variables first then plug in values/arbritary values at end to get the final answer. 
Agreed that it is definitely much easier to catch mistakes in variable form.