The statements that are true are:
First option: All functions have dependent a variable
Second option: All functions have an independent variable.
Fifth option: A horizontal line is an example of a functional relationship
You can solve this using proportion.
5 = 4
7 = ?
7(4)/5= 5.6
7 cakes cost £5.6
7x + 14 + 3x + 15 = 14x + 14 + 2
10x + 14 = 14x + 16
14 - 16 = 14x - 10x
-2 = 4x
X = - 2/4
X = - 1/2 OR X = - 0.5