X| 1 | 15 | 225 |
y| 4 | ? | 900 |

therefore
[tex]\dfrac{4}{1}=4;\ \dfrac{900}{225}=4;\ \dfrac{?}{15}=4\to?=60[\tex]
Answer: ? = 60
Answer:
11. This is counting only odd numbers, or counting by two starting with one.
<span> Use the substitution method to justify that the given system of equations has no solution.</span>