Final answer:
To solve the formula d=a-2b for a, we need to isolate a on one side of the equation. The principal, p, when i=$5,600, r=4%, and t=7 years in the formula i=prt is $20,000.
Step-by-step explanation:
To solve the formula d=a-2b for a, we need to isolate a on one side of the equation. We can do this by performing the inverse operation of subtracting 2b, which is adding 2b to both sides of the equation.
d + 2b = a - 2b + 2b
d + 2b = a
So, the value of a is equal to d + 2b.
Now, let's apply this formula to find the principal, p, when i=$5,600, r=4%, and t=7 years in the formula i=prt. Rearranging the formula, we have:
p = i / (rt)
Substituting the given values, we have:
p = 5600 / (0.04 * 7)
p = 5600 / 0.28
p = 20000
So, the principal is $20,000.