In order to solve this, you have to set up a systems of linear equations.
Let's say that children = c and adults = a
30a + 12c = 19,080
a + c = 960
I'm going to show you how to solve this system of linear equations by substitution, the easiest way to solve in my opinion.
a + c = 960
- c - c
---------------------- ⇒ Step 1: Solve for either a or c in either equation.
a = 960 - c
20(960 - c)+ 12c = 19,080
19,200 - 20c + 12c = 19,080
19,200 - 8c = 19,080
- 19,200 - 19,200
---------------------------------- ⇒ Step 2: Substitute in the value you got for a or c
8c = -120 into the opposite equation.
------ ---------
8 8
c = -15
30a + 12(-15) = 19,080
30a - 180 = 19,080
+ 180 + 180
-------------------------------
30a = 19,260
------- -----------
30 30
a = 642
__________________________________________________________
I just realized that there can't be a negative amount of children, so I'm sorry if these results are all wrong.
Answer:
2 x minus y = negative 6 and 3 x minus y = negative 5
Step-by-step explanation:
y = 2(x+3) = 2x + 6 or 2x - y = -6
y = 5 + 3x or 3x - y = -5
Lets split the box in pieces and then add:
top = 20*15 = 300
sidesA = 2*20*9 = 360, is multiplied by 2 cause there are 2 sides like this
sidesB = 2*9*15 = 270, is multiplied by 2 cause there are 2 sides like this
so in total we have:
total = 300 + 360 + 270 = 930 cm^2
if we express this quantity in mm^2 we have:
<span>1cm² = 100 mm²</span>total = 930*100 = 93000 mm^2
so if the tiles are 5 mm^2 we need:
total tiles = <span>93000/5 = 18600
we need 18600 tiles of 5 mm^2</span>
