Help I really don't know how to do this I need help

Choose the graph that matches the following system of equations: 7x + 2y = −6 6x − 7y = 21 a line includes points negative 2 comma 4 and 0 comma negative 3. a line includes points 6 comma 2 and 0 comma negative 3 a line includes points 0 comma negative 3 and 6 comma 2. a line includes points negative 2 comma 1 and negative 3 comma 4 a line includes points 0 comma negative 3 and negative 1 comma 4. a line includes points 0 comma negative 3 and negative 1 comma 3 a line includes points 0 comma 3 and negative 1 comma negative 3. a line includes points 0 comma negative 3 and negative 2 comma 4.

Prove sin2a + cos2a - 1 / sin2a + cos2a + 1 = 1 - tana / 1 + cota

What is the solution for 6 - 7/8? explain the steps.