Multiply (length) times (width). For a square, both numbers will be the same.
1 + 10 + 18 = (1 + 10) + 18
1 + 10 + 18 = 11 + 18
1 + 10 + 18 = 29
OR
1 + 10 + 18 = 1 + (10 + 18)
1 + 10 + 18 = 1 + 28
1 + 10 + 18 = 29
The problem above can be modelled as shown in the graph below
At

, the height of the water from the ground is

2>8-4h/3 subtract 8 from both sides
-6>-4h/3 multiply both sides by 3
-18>-4h divide both sides by -4 (and reverse sign because of division by a negative value)
4.5<h or by convention...
h>4.5
Answer:
c) 1,381.5.
Step-by-step explanation:
First term = 3.1 *1 - 2 = 1.1
2nd term = 3.1*2 - 2 = 4.2
3rd term = 3.1*3 - 2 = 7.3
so the common difference d = 3.1.
S30 = (30/2) [ 2* 1.1 + (30-1) * 3.1)]
= 1,381.5.