Corresponding measures have the same ratio.
.. (x -1)/4 = (2x +1)/10
.. 5(x -1) = 2(2x +1) . . . . . . multiply by 20
.. 5x -5 = 4x +2 . . . . . . . . eliminate parentheses
.. x = 7 . . . . . . . . . . . . . . . add 5 -4x
x = 7
104 Because 100*4 = 400 and 4*4 = 16 so add together and get 416
The answer is an Interval.
Hope this help.
If it is

=2c+9, go to AAAAAA
if it is (

)(4c+16)=2c+9, go to BBBBB
AAAAAAAAA

=2c+9

=2c+9
times 4c+16 to both sides
1=(2c+9)(4c+16)
distribute
1=8c^2+68c+144
minus 1 both sides
0=8c^2+68c+143
use quadratic formula
c=

or

BBBBBBBBBBBB
(3/3)(4c+16)=2c+9
1(4c+16)=2c+9
4c+16=2c+9
minus 2c both sides
2c+16=9
minus 16 both sides
2c=-7
divide both sides by 2
c=-7/2
c=-3.5
if it is

=2c+9,
c=

or

if it is (

)(4c+16)=2c+9, c=-3.5
Katrice paid 46 dollars in total bc the free watermelon doesn't change a thing, just how many slices I would eat at the party. lol ;)