Step-by-step explanation:
oh, come on ! one is finding the inequality itself, the other is solving it. you don't know the difference of that ?
if so, please let me know, what you don't understand of the following explanations, so that I can add whatever is necessary.
you know, what an equality (ahem, equation) is ?
both, equations and inequalities are like a balancing scale with usual different things on the two pans left and right.
an equation is when both sides are in balance. their weight is equal.
an inequality is, when one side is heavier than the other.
and you know, what a variable is ? it is a kind of placeholder for actual values. it is like keeping some space open on the scale pan with a list of conditions for what kind of things you can put in that open space, so that the status of the scale stays unchanged.
A
twenty less than a number is at least 15
looks mathematically
x - 20 >= 15 (larger or equal = "at least")
B
x - 20 >= 15
x >= 35
so, this is true for
{x € R | x >= 35}
or
{x € R | x = 35 or x > 35}
so, this is true for all real values of x that are at least 35.
