X+Y=2300
1.25 x+0.75y = 2300 * 1. 15 .
The solution is X= 1840. The existing number of boys is 1.25X=2300.
2. If the values of x and y are opposite, then y =-x .. Substitute into the equation:
X+2X=-2a
2X-5X=a+6
The solution is a=6.
3. If the solutions of the two equations are the same, then four straight lines intersect at the same point. (number-shape combination method)
Then 2x+5y =-6; The intersection (2, -2) of 3X-5Y= 16 can be obtained by solving two sets of equations.
So substitute the intersection into the other two equations and you get:
2a+2b=-4
2b-2a=-8
The solution is a= 1 and b=-3.
So the 20 12 power of (2a+b) is equal to the 20 12 power of (-1) is equal to 1.
For masquerade, because boys can't see themselves, X- 1 should be set as the equation when all boys are X.
Similarly, girls can't see themselves, and y must be reduced by 1.
Let all boys be X and all girls be Y.
Then Y=2(X- 1)+ 1.
3/5(Y- 1)=X
X=6,Y= 1 1。