Let's say hmm let's use the figures in thousands, so
model A costs 90 + 4 per year, so... ok.. after "t" years, then the cost for model A is then 90 + 4*t, or
A = 90 + 4t.
now, model B is 70 + 10 per year, so,... after "t" years, model B is then
B = 70 + 10 * t, or
B = 70 + 10t.
if we were to assume A < B, namely the cost of A is less than B, what would the years be? namely, what's "t"?

after that period, then A becomes cheaper than B.
Answer:
53/5
Step-by-step explanation:
since 10 is the denominator of the denominator we can move it to the numerator, giving us 10n/5-3n = 1/5
multiply all sides by 5-3n, giving us 10n = (5-3n)/5
now multiply by 5 to get rid of the final denomintor, 50n = 5-3n
move 3n to the other side 53n = 5, n = 53/5
The first answer is the correct one
First you subtract 9x from y and you get 45 - 9x = -y and you don't want negatives so you switch all the signs to get y = -45 + 9x