19/42 x 5/5 = 95/210
13/70 x 3/3 = 39/210
95/210 + 39/210 = 134/210
134/210 = 67/105
13/42
18/35 + 13/42 = 1211/1470 or 173/210
13/14 + 5/6 = 39/42 + 35/42 = 74/42 = 37/21 or 116/21
Oh, dude, it's like basic math, right? So, if you're trying to figure out what plus 13 equals 42, you just subtract 13 from 42 and you get... wait for it... 29! Boom, math wizard over here!
18/35 + 13/42 = 108/210 + 65/210 = 173/210
-55
42+(-29) = 13
105.
(7 x 6) + (7 x 13) = 7 x 19 = 133
42 over 26 can be simplified as 21 over 13
12/70 - 19/42 = 0.17142 - 0.45238 = -0.28096
13/42 = 0.3095238 recurring (that is, 0.3095238095238...)