Suppose

At the same time, we can write

Note that
(just reverse the sum). Let's pair the first terms of
and
, and the second, and the third, and so on:

Now, each grouped term in the sum on the right side adds to 151. There are 52 grouped terms on that same side (because there are 50 numbers in the range of integers 51-100, plus 50 and 101), which menas

But
, as we pointed out, so

So, I'm assuming that the x represents multiplication...
Because multiplication has a higher precedence over addition, we'll multiply the numbers first:
18 + 48
Then we simply add:
66
X/2=8/9 | *2
x=16/9≈ 1,78
2. 1 $.........1,09 Euro
x$...........157 Euro
x=157*1/1,09≈144,04 $
If she rides at 12 miles per hour, we know that 45 minutes is three quarters of an hour, therefore just workout:
3/4 x 12 = 9
So she would travel 9 miles in 45 minutes.