I think the answer is 3/2 but i am not sure
The irrational in between should be 7.8
a. The first variable is x and the second variable is y.
b. The equations are
and 
Step-by-step explanation:
Step 1:
The first step is to define the variables. The variables can be any two symbols, letters, characters, etc.
Here let the first variable be x and the let the second variable be y.
So the variables are defined as x and y.
Step 2:
The sum of the given variables is 12.
The first variable + the second variable = 12,

The difference between the two variables is 4.
The first variable - the second variable = 4.

Step 3:
If we add both the equations we get,
and 
x = 8 and y = 4.
So base on your question the possible answer to that kind of question and the solution are the following and i hope you will understand the formula and free to ask some questions if needed.
<span>2<span>cos2</span><span>x2</span>=1+cosx=1−<span>1517</span>=<span>217</span>,<span>cos2</span><span>x2</span>=<span>117</span></span>
<span>cos<span>x2</span>=−<span>1<span>17<span>−−</span>√</span></span>....(1)</span>
<span>sin<span>x2</span>=<span>1<span>17<span>−−</span>√</span></span>,90<<span>x2</span><135</span>
<span>sin<span>x2</span>>0,cos<span>x2</span><0,tan<span>x2</span><0</span>
<span>2<span>sin2</span><span>x2</span>=1−cosx=1−<span><span>−15</span>17</span>=<span>3217</span>,sin<span>x2</span>=<span>4<span>17<span>−−</span>√</span></span>.....(2)</span><span>
divide (2) by (1) and get the value of tan x/2</span>
Answer:
x = 30
Step-by-step explanation:
Put in proportions
= 
Cross multiply and get 27x = 45 x 18
OR...
27x = 810.
THEN...
divide by 27 on both sides to get 30
x = 30