Explanation:
remember, to transform an equation we need to apply any operation to both sides of the equation. otherwise the equality relation is destroyed.
we want to get the equating to look like " x = ..."
so, the "+ 39" is in the way.
we need to subtract 39, but as mentioned, we need to do this on both sides.
x + 39 = 74
x + 39 - 39 = 74 - 39
x = 35 in
the fig tree is therefore 35 in. that is 39 in shorter than 74 in (the orange tree).