Question 1040159
This is a very common exercise question type.

<a href="https://www.algebra.com/my/Mixtures%3A-All-in-Symbols.lesson?content_action=show_dev">Mixing two concentrations for known amount of mixture</a>

<a href="https://www.youtube.com/watch?v=-REjxT9KCzQ">video example , two part mixture problem using just one variable</a>