Assuming LCD means Lowest Common Denominator
Assuming by "and" you mean adding the two
Well, you go by the multiples of 7;
7, 14, 21, 28, 35, 42, 49, 56, 63,<u> 70</u>
Multiples of 10;
10, 20, 30, 40, 50, 60, <u>70</u>, 80, 90, 100
Straight away you can see the lowest common multiple is 70,
Now to go about adding them,
2/7 * 10 (both sides) , 20/70
9/10 * 7 (both sides) , 63/70
Then you add the two; 20/70 + 63/70  - now we can add them because they share the same denominator
20/70 + 63/70 = 83/70 = 1 whole 13/70 (simplified)
<u>The LCD is 70
Quick tip, </u>to find a common multiple (not necessarily the lowest) multiply the two denominators. 
        
                    
             
        
        
        
Answer:
104°+33°+(5x+13)°=180°[all angle sum is 180°]
137°+(5x+13)=180°
137°+13+5x=180°
150°+5x=180°
5x=180°-150°
5x=30
x=30/5
×=6
 
        
                    
             
        
        
        
Answer:
x+2y=- 7
x-2y =9
Step-by-step explanation:
Solving Steps
2x+4y=-14
x-2y=9
Divide both sides
(2x+4y) ÷2=-14=2
{x-2y=9
Remove the parentheses
Divide
2x÷2+4y÷2=-7
x-2y =9
Divide
Solution
x+2y=- 7
x-2y =9
 
        
                    
             
        
        
        
Answer:
1.2 hours 
Step-by-step explanation:
Recall :
Distance = speed * time
Let the time taken = x
Creating an equation for the question :
Distance of train A + Distance of train B = 192
70 * x + 90 * x = 192
70x + 90x = 192
160x = 192
x = 192 / 160
x = 1.2
It takes 1.2 hours to be 192 miles apart.