$78.90 = n(.05)+d(.10)

The below explanation can give you whatever you are seeking.

Step-by-step explanation:

The two unknowns in the equation are "n" and "d"

$78.90 = n(.05)+d(.10) ........................ (1)

Make both unknowns the subject of the formula and substitute for each other

............................ (2)

also

............................ (3)

You can substitute for either "n" or "d" in equation (1),

Putting equation (3) into (1)

78.90 = n(.05) +

78.90 = n(.05) + 78.90 - n( .05)

collecting all like terms

78.90 - 78.90 = n(.05) - n(.05)

0 = n(.05 - .05)

0/0 = n

n  is undefined

Putting equation (2) into (1)

78.90 =   + d(.10)

78.90 = 78.90 - d(.10) + d(.10)

78.90 - 78.90 = - d(.10) + d(.10)

0 = d (-.10 + .10)

0/0 = d

d is also undefined

guess at question:

a vertical line intersects the graph of g(x,y) = 0 at two points. what conclusion follows about the function f(x) implicitly defined by g(x,f(x)) = 0?

the domain of f(x) cannot include the x coordinate of any such vertical line.

informally, f(x) is not a function, and

g(x,y)=0 cannot be solved for y uniquely.

the relation r = {(x,y) such that g(x,y) = 0} is a function if

for all (a,b) ∊ r and (c,d) ∊ r, a=c implies b=d.

step-by-step explanation: