This is a simple interest formula computation.
Given:
Interest = 826
Interest rate = 2.6%
term = 7 years.
The simple interest formula is:
Interest = Principal * Interest rate * term
To solve for the principal:
Principal = Interest / (Interest rate * term)
Principal = 826 / (2.6% * 7)
Principal = 826 / 18.2%
Principal = 4,538.46
To check: Solve for the interest
I = 4,538.46 * 2.6% * 7
I = 117.999 * 7
I = 825.993 rounded up to 826.