。
I'll call you as soon as we figure out the answer.
Literal
We [to-に] answer [subject-が] understand-[if-たら] immediately phone [emphasis-よ].
僕たちに分かる ('we understand') — 分かる is an intransitive state verb, so the understander is marked with に (experiencer) and the understood thing with が. たら is a conditional/temporal marker — 'when/if [clause], then.' すぐに ('immediately') and the final よ create a friendly assurance.