This isn't how that problem was meant to be solved - it's meant to be a straightforward subtraction problem. For instance, this is a US 2nd grade subtraction word problem from Khan Academy:
Sparky the dragon was born with 28 spikes. He grew several more spikes as he got older. Now Sparky has 80 spikes. How many new spikes did Sparky grow?
Sure, this could be expressed as an algebra problem, 28 + X = 80, but the intention here is quite clearly for the student to see it as a subtraction problem.
Sparky the dragon was born with 28 spikes. He grew several more spikes as he got older. Now Sparky has 80 spikes. How many new spikes did Sparky grow?
Sure, this could be expressed as an algebra problem, 28 + X = 80, but the intention here is quite clearly for the student to see it as a subtraction problem.
https://www.khanacademy.org/math/cc-2nd-grade-math/cc-2nd-ad...