Answer:
(x, y) = (3, 5)
Step-by-step explanation:

Solving by elimination here again, there are 2 good options available. Either multiply the whole bottom equation by -1 to cancel the x, or by 2 to cancel the y. I'll do the latter:

Add from top to bottom:

Now, with the value of x, solve for y in either of the equations. I'll choose the second one here:

(x, y) = (3, 5)
X - y = 5
x = y + 5
y = x - 5
She used 54 inches. 3/4 is equal to .75 so you can find 3/4 of the board by taking the fool length and multiplying it by .75 so 6•.75=4.5. So 3/4 of the board is 4.5 ft. However, the answer has to be in inches so since there are 12 inches in a foot you multiply 4.5•12 and that gives you your answer:54 inches.
15.80 * 1.05 should give you the answer
A method to solve it would be would be:
First converting 5% to a decimal then multiplying that by 15.80 in order the find 5 percent of 15.80...Afterwards you have to add that value to the original 15.80 ..And you should end up with the same answer.