Answer:
Step-by-step explanation:
its c=5
6y+18+3=51
6y+21=51
6y=51-21
6y=30
y=5
Answer:
See explanation
Step-by-step explanation:
Given 
According to the order of the vertices,
- side AB in triangle ABC (the first and the second vertices) is congruent to side AD in triangle ADC (the first and the second vertices);
- side BC in triangle ABC (the second and the third vertices) is congruent to side DC in triangle ADC (the second and the third vertices);
- side AC in triangle ABC (the first and the third vertices) is congruent to side AC in triangle ADC (the first and the third vertices);
- angle BAC in triangle ABC is congruent to angle DAC in triangle ADC (the first vertex in each triangle is in the middle when naming the angles);
- angle ABC in triangle ABC is congruent to angle ADC in triangle ADC (the second vertex in each triangle is in the middle when naming the angles);
- angle BCA in triangle ABC is congruent to angle DCA in triangle ADC (the third vertex in each triangle is in the middle when naming the angles);
The answer is: 12 centimeters.
The explanation is shown below:
1. By definition, all four sides of the square are equal and the diagonals are equal too.
2. Keeping the information above on mind, you know that AC and BD are equal:

3. Then, the length of BD is twice BE. So, you can calculate it as following:


4. Therefore, the lenght of AC is:

Answer:
18
Step-by-step explanation:
15 x 2 = 30
30 - 12 = 18
18 girls are in his class