S = sisters ages
M =2S +7
M=13
13 = 2S+7
subtract 7 from each side
6 = 2S
divide by 2
3=S
sisters age is 3
75.
Explanation: from 3 to 12, you add 9, and then double the 12 to get to 24, and then add 9 again to get to 33, and double it to get 66, so the pattern is to add 9 and then double.
You need to add the two quadratics together...
x^2+11x-6+6x^2-3x+9
7x^2+8x+3
Answer: 3:1
Step-by-step explanation: