Answer:
-90
Step-by-step explanation:
10+5×5×(-2)
10+25×(-2)
10+(-100)
10-100
-90
You bring the numerals on to the other side of the equation, therefore dividing 19 by 3 and 6.
3x + 6y = 19
3x + y = 19/6
x + y = 3.17/3
x + y = 1.1
8+7=15
300/15=20
8 x 20 =160 Boys
7 x 20 = 140 girls
140 + 160 = 300
Hope this helps!
Step-by-step explanation:
Starting with the first one, we know that 3²=9 and 4²=16, so √10 is between 3 and 4. Similarly, √27 is a little over 5. √3 is close to 2, √2 is close to 1, and √9=3, so for simplicity, we can write this as 
The 3.something and the 3 kind of cross out, and we're left with 5.something over 2 1.somethings, which can be closer to 2 or 1, which is somewhat unclear -- therefore, our answer can be D or E, and we'll wait on this one
For the second one, we can cross out the √6s to get
-- π is a little greater than 3, so this is E, making the first one D
For the third one, we can cross out the √3 to get (3-2)/2 = 1/2, or A as it is between 0 and 1
For the last one, note the multiplication -- cross out the √3 to get (3*2√2)/6, and we get 6√2/6=√2, or C
False
They also have symmetry over their minor axis.