A+B=15 —>A+15=B(plug this into the other equation)
60a+30b=600
60a+30(a+15)=600
60a+30a+150=600
90a+150=600
90a=450
A=5 (plug back in to first equation)
A+B=15
5+B=15
B=10
They have 5 of the Model A and 10 of model B.
If I remember correctly it is equal
Answer:

Step-by-step explanation:
- this can be done by simple manipulation .
- in the given equation, A is the subject.
- so, by the above statement you can understand the meaning of making something as a subject.
- given equation: A = 1/2 bh
- multiply both the sides by 2,
2A = bh
- divide both the sides by h,

so, the required form is : 
The sum of all angles (around the black dot) is 360°
All 5 angles (if you forget the red line) are the same; so each angle is 360°/5 = 72°
So Angle 1 is 72°