(a)

(b)we have 4 terms in this expression.
(c)+12 is the leading coefficient in

(d) constant is -45
This should help just try to use this
numerator = top part of the fraction
denominator = bottom part of the fraction
* means multiply
a.
you can only add the numerator when the denominator is the same
cant add the denominator
denominator has to be the same
1/5 = 4/20
4/20 + 7/20 = 11/20
b.
1 7/8 = 15/8
3/4 ÷ 15/8 =
3/4 * 8/15 =
24/60 = divide both top and bottom by 12 =
2/5
"He starts both trains at the same time. Train A returns to its starting point every 12 seconds and Train B returns to its starting point every 9 seconds". Basically, what you need to do is find the least common multiple. The least common multiple of 12 and 9 is 36, so the least amount of time, in seconds, that both trains will arrive at the starting points at the same time is 36 seconds.