9 because twice as many means x times 2; if there are 18 girls, divide by 2 and you get 9. Nine times two is 18. :)
Answer:
x = 4
Step-by-step explanation:
1.3x - 10 = 0.8x - 8
Add 10 to both sides.
1.3x = 0.8x + 2
Subtract 0.8x from both sides.
0.5x = 2
Divide by 0.5.
x = 4.
Proof:
1.3x - 10 = 0.8x - 8
1.3(4) - 10 = 0.8(4) - 8
5.2 - 10 = 3.2 - 8
-4.8 = -4.8
For question 1 it would be 10 hundreds and 2 tens for the second question it would be 13 hundreds