We can work it out with arithmetic, or with algebra.

Eg.

```
a = 100
b = 6.75 / 100 # 0.0675
c = a * b # 6.75
d = a + c # 106.75
e = 15 / 100 # 0.15
f = d * e # 16.0125
g = d + f # 122.76
```

That's the long and drawn out approach. Let's work it backwards and see if we can simplify it with a little algebra.

```
g = d + f => but d = a + c
g = a + c + f => but f = d * e
g = a + c + e * (a + c)
g = (a + c) * (1 + e) => but c = a * b
g = (a + a * b) * (1 + e)
g = a * (1 + b) * (1 + e)
g = 100 * (1 + 0.0675) * (1 + 0.15)
g = 100 * 1.0675 * 1.15
g = 106.75 * 1.15
g = 122.76 (rounded to two decimal places)
```

This looks convoluted, I know. Study it closely. It comes down to

` meal * 1.0675 * 1.15`

Since we have two constant factors, we can multiply them out to arrive at a coefficient that will apply to all meals.

`1.0675 * 1.15 == 1.227625`

which we can round to `1.2276`

so that,

`meal_cost = meal * 1.2276`