My apologies for the dumb question. I was wrapping my head around this question - listed below. I’m a bit confused as to why when we have 2C equal 3D units and are trying to convert from a D unit to a C unit we don’t leverage 3/2 and are required instead to leverage 2/3.
I have a feeling I’m stuck thinking in Algebra terms - is the rule then when dealing with tangible objects and trying to do conversions we should do basic ratio?
On Mars, 3A equal 5B units, while 4B units equal 7C units - lastly 2C units equal 3D units. How many A units equal 35D units?
You are on the right track. Here on Earth $2.54$cm is the same length as $1$ inch. That means the fraction $$ \frac{2.54 \text{ cm}} {1 \text{ inch}} = 1. $$ a dimensionless number. So to find out how many cm in a foot you can calculate $$ 1 \text{ foot} \times \frac{12 \text{ inch}} { \text{ foot}} \times \frac{2.54 \text{ cm}} {1 \text{ inch}} = 2 \times 2.54 \text{ cm} , $$ cancelling the unit names as if they were algebraic variables.
Do the same on Mars, where $2C/3D = 1$ and $3D/2C = 1$. Use whichever of those makes the units cancel as you wish. Don't try to figure out $2/3$ versus $3/2$.