Santiago Ortiz runs a small farmer's market every Saturday. He deposits last Saturday's receipts into his savings account. In bills he had 19 one hundreds, 11 fifties, 22 tens, 34 fives, and 168 ones. Change included 2 one-dollar coins, 2 fifty-cent pieces, 72 quarters, 290 dimes, and 78 pennies. He also deposited checks for $32.11, $12.93, and $52.11. He wants to receive
$50 in cash. What is his total deposit?

We have that the sum of two numbers  is 9

this can be written as:

x + y  = 9

where x is the larger number.

Now we want to write:

"the difference between one more than the larger number and twice the smaller number"

First, remember that the difference between A and B is:

A - B

Then "the difference between one more than the larger number and twice the smaller number"

is:

"one more than the larger number" = ( x + 1)

"twice the smaller number" = 2*y

the difference between these is:

(x + 1) - 2*y

Now we can simplify:

We know that:

x + y = 9

then:

y = 9 - x

replacing that in the equation:

(x + 1) - 2*y

we would get:

x + 1 - 2*(9 - x)

x + 1  -18 + 2x

(x + 2x) + (1 - 18)

3x - 17

This means that we can write:

"the difference between one more than the larger number and twice the smaller number"

as: 3x - 17