Evaluate seven 𝑥 plus five when 𝑥
is equal to 10.
So we’re told that 𝑥 is equal to
10 and wherever we see 𝑥 in our expression, we have to replace that with 10. But we have to think quite
carefully. We don’t just literally write 10
because that would then be 710 plus five. Well, that seven 𝑥 means seven
times 𝑥. So we have to think about what the
expression actually means before we substitute those numbers in. So seven 𝑥 plus five means seven
times 𝑥 plus five. So when 𝑥 is 10, that means seven
times 10 plus five. Now, if you think about your order
of operations, you do multiplication and division before you do addition and
subtraction. So we’re going to evaluate this
first. Now, seven times 10 is 70. So that’s 70 plus five, which gives
us an answer of 75.