Highlight all instances of parallel structure. there is no longer any room for hope. if we wish to be free—if we mean to preserve inviolate those inestimable privileges for which we have been so long contending—if we mean not basely to abandon the noble struggle in which we have been so long engaged, and which we have pledged ourselves never to abandon until the glorious object of our contest shall be obtained—we must fight!

"If we wish to be free-if we mean to preserve", "if we mean not basely to abandon" AND "which we have been so long contending", "which we have been so long engaged", "which we have pledged".

Parallelism is the repetition of the same grammatical structure. There are two instances of parallel structure in this excerpt. The first is the "If we ___ to ___" structure. The second is the "which we have " structure. By filling the passage with this parallel structure is gives the sense of a list of reasons that all, compounding on top of one another, logically lead to the need to fight. The change from the parallel structures in the last line "we must fight!" makes this exclamation stand out and hold power.  

the answer is a . the absence of love

substitute y = 2x - 4 to x + 2y = 12:

x + 2(2x - 4) = 12     use distributive property

x + (2)(2x) + () = 12

x + 4x - 8 = 12     add 8 to both sides

5x = 20     divide both sides by 5

x = 4

put the value of x to the first equation:

y = 2(4) - 4

y = 8 - 4

y = 4