In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Problem: find value for x from below equation ? x + 1 = 4 
Options: a ) - 5 , b ) - 4 , c ) 4 , d ) 3 , e ) 2
d

Problem: cost is expressed by the formula tb ^ 4 . if b is doubled , the new cost is what percent of the original cost ? 
Options: a ) 200 , b ) 600 , c ) 800 , d ) 1600 , e ) 50
d

Problem: the number of positive integer solutions for the equation x + y + z + t = 15 is 
Options: a ) 654 , b ) 584 , c ) 384 , d ) 364 , e ) 394

d