1.) set up a w_k_u chart
2.) in the w column write in on top and mi in the bottom like this
w_K_U
in_
mi_
then in the k column write 2 for in and 15 for mi
W_K_U
in_2_
mi_15_
then in the U column, you write 7 for in and x for mi
W_K_U
in_2_7
mi_15_x
then cross multiply: 2x = 15(7)
multiply 15 times 7 which is 105
2x=105
divide 2x by 2
x=105
answer 105
42
let the smallest even number be x, than the four even numbers are x, x+2, x+4, x+6, their sum is 180
x+x+2+x+4+x+6=180
4x+12=180
4x=168
x=42
the smallest even number is 42.
1 = 1 x 1
1 factors
2 = 1 x 2
2 factors
3 = 1 x 3
2 factors
4 = 1 x 4
4 = 2 x 2
3 factors
5 = 1 x 5
2 factors
6 = 1 x 6
6 = 2 x 3
4 factors
7 = 1 x 7
2 factors
8 = 1 x 8
8 = 2 x 4
4 factors
9 = 1 x 9
9 = 3 x 3
3 factors
10 = 1 x 10
10 = 2 x 5
4 factors
11 = 1 x 11
2 factors
12 = 1 x 12
12 = 2 x 6
12 = 3 x 4
6 factors
13 = 1 x 13
2 factors
14 = 1 x 14
14 = 2 x 7
4 factors
15 = 1 x 15
15 = 3 x 5
4 factors
16 = 1 x 16
16 = 2 x 8
16 = 4 x 4
5 factors
17 = 1 x 17
2 factors
18 = 1 x 18
18 = 2 x 9
18 = 3 x 6
6 factors
19 = 1 x 19
2 factors
20 = 1x 20
20 = 2 x10
20 = 4 x 5
6 factors
So they are 6, 8, 10, 14 and 15 on the number line
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
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![\bf \cfrac{x}{4x+x^2}\implies \cfrac{\begin{matrix} x \\[-0.7em]\cline{1-1}\\[-5pt]\end{matrix}}{\begin{matrix} x \\[-0.7em]\cline{1-1}\\[-5pt]\end{matrix}~~(4+x)}\implies \cfrac{1}{4+x}\qquad \{x|x\in \mathbb{R}, x\ne -4\}](https://tex.z-dn.net/?f=%5Cbf%20%5Ccfrac%7Bx%7D%7B4x%2Bx%5E2%7D%5Cimplies%20%5Ccfrac%7B%5Cbegin%7Bmatrix%7D%20x%20%5C%5C%5B-0.7em%5D%5Ccline%7B1-1%7D%5C%5C%5B-5pt%5D%5Cend%7Bmatrix%7D%7D%7B%5Cbegin%7Bmatrix%7D%20x%20%5C%5C%5B-0.7em%5D%5Ccline%7B1-1%7D%5C%5C%5B-5pt%5D%5Cend%7Bmatrix%7D~~%284%2Bx%29%7D%5Cimplies%20%5Ccfrac%7B1%7D%7B4%2Bx%7D%5Cqquad%20%5C%7Bx%7Cx%5Cin%20%5Cmathbb%7BR%7D%2C%20x%5Cne%20-4%5C%7D)
if you're wondering about the restriction of x ≠ -4, is due to that would make the fraction with a denominator of 0 and thus undefined.
