I would argue that this is a poorly specified puzzle (as is common with these things). @MacGyver88's solution is completely valid. But you could equally say
In fact, if you assume that this is a column-by-column operation, you could set up a system of simultaneous equations to figure out what that operation was (assuming it was linear which is not ...
7 is the value for g, which is the first letter of "green", the sum of the values of the letters in the word is 49, and "3" is for "cube", 49^3=117649.
Just like "19" is for "square" refering to squaring
"[red]" and "[yellow]"
For sake of completeness, I have done a computer search and have found that 40 $\tau$s is the absolute minimum one can achieve. This can be done using Ian's expressions for 1–13 and 17–20, KSmarts' expression for 15, and two new expressions for 14 and 16:
The only expressions requiring 3 $\tau$s are those for 11, 19, and 20, and exhaustive search has shown ...
to move 3000 bananas by 1 km, camel consumes 5 bananas which with five trips. so not when number of bananas are less than or equal to 2000 the trips required is 3.
so to consume 1000 bananas
5x = 1000
move 3000 bananas for x=200 miles ( 5 trips). we are left with 2000 bananas.
now we have 2000 bananas and we can move bananas in 3 trips