6-(-5r)=5r-3,12p-7=-3p+8,-7+4m=6m-5,8-9t=21t-17,
Answer (1) 6-(-5r)=5r-3,
=> 6 - ( + 3 ) = 5r + 5r
=> 3 = 10r
=> therefore; r = 3/10
Answer (2) 12p-7=-3p+8,
=> 12p +3p = +8 +7
=> 15p = 15
=> therefore, p = 1
Answer (3) -7+4m=6m-5,
=> -7 + 5 = 6m - 4m
=> 2 = 2m
=> therefore; m = 1
Answer (4) 8-9t=21t-17,
=> 8 + 17 = 21t + 9t
=> 25 = 30 t
=> t = 25/30
therefore; t = 5/6 (simple form)