Okay, straight-up calling shenanigans on this one.
If we are to assume that each bottle displayed represents "1" bottle in all four lines, why does that not apply to the other displayed items?
In the second line, for the mathematics to work out correctly, each single keg/drum is equal to "2"... BUT there are not 4 kegs/drums displayed in total; only 2 are shown.
Similarly, in the third line, there appears to be 8 bundles of bills in each pile (to be fair, some might be hidden 'behind' the pile, but we will disregard that possibility), yet they are supposed to represent the value of "5"; that would mean each single bundle of bills is equal to 5/8, but there are 8 individual bundles of bills displayed in total, not a mere 5 bundles...
The only thing we can say for certain is that solving for d is unknowable, because we've now introduced a new variable, e, which is represented by the picture of 7 bottles in line three and which is not the same variable that a represented for the six bottles in lines one, two and four.
(I know, I know; overthinking it here...)
Me. I had the CASIO fx-7700G while in college:
https://www.calculator.org/calculators/ ... 7700G.html