Currently, the sum of the ages of yumi, rana, and victoria is 42 years. four years ago, the sum of the ages of rana and victoria was equal to the current age of yumi. what is yumi's current age?

Let's introduce variables for these ages: y,r,v.

y+r+v=42 (Currently, the sum of the ages of Yumi, Rana, and Victoria is 42 years)

r-4+v-4=y (Four years ago, the sum of the ages of Rana and Victoria was equal to the current age of Yumi.)

we add up what we can
r+v=y+8

now, we know that
r+v=y+8 and y+r+v=42
so we can substitute what we know about r+v into the first equation

y+(r+v)=42
y+(y+8)=42
2y=42-8
2y=34
y=17

yumi is 17 now!

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.