let's firstly, convert the mixed fractions to improper, and then do equation.
![\bf \stackrel{mixed}{3\frac{4}{5}}\implies \cfrac{3\cdot 5+4}{5}\implies \stackrel{improper}{\cfrac{19}{5}} ~\hfill \stackrel{mixed}{2\frac{5}{7}}\implies \cfrac{2\cdot 7+5}{7}\implies \stackrel{improper}{\cfrac{19}{7}} \\\\[-0.35em] \rule{34em}{0.25pt}](https://tex.z-dn.net/?f=%5Cbf%20%5Cstackrel%7Bmixed%7D%7B3%5Cfrac%7B4%7D%7B5%7D%7D%5Cimplies%20%5Ccfrac%7B3%5Ccdot%205%2B4%7D%7B5%7D%5Cimplies%20%5Cstackrel%7Bimproper%7D%7B%5Ccfrac%7B19%7D%7B5%7D%7D%0A~%5Chfill%0A%5Cstackrel%7Bmixed%7D%7B2%5Cfrac%7B5%7D%7B7%7D%7D%5Cimplies%20%5Ccfrac%7B2%5Ccdot%207%2B5%7D%7B7%7D%5Cimplies%20%5Cstackrel%7Bimproper%7D%7B%5Ccfrac%7B19%7D%7B7%7D%7D%0A%5C%5C%5C%5C%5B-0.35em%5D%0A%5Crule%7B34em%7D%7B0.25pt%7D)

Answer:
a>0
Step-by-step explanation:
if a is negative then the subtraction sign would switch. therefore, for the expression to have a negartive value a must be greater than 0
First get y by its self , then graph , find intersection point and plug in x and y to both equations, see if it makes sense , then the solution must be you intersection point
Correct answer is the 3rd one.
The sum of the interior angles is 360