# What algebraic expressions are 列式表示比a的5倍大4的数与比a的2倍小3的数 and 列式表示比x的7倍大3的数与比x的6倍小5的数 asking for?

In my grade-7 maths textbook (image), we have the problem:

1. 列式表示比a的5倍大4的数与比a的2倍小3的数，计算这两个数的和；
列式表示比x的7倍大3的数与比x的6倍小5的数，计算这两个数的差。

I'm not quite sure what this means, although I'm fairly sure the first parts state (in words) two quantities involving variables (it's in the algebra section), and the second part asks for the sum (和) or difference (差). I thus think it wants `(5a+4) + (2a-3)` and `|(7x+3) - (6x-5)|` (where `|...|` denotes absolute value (绝对值)) but I'm not sure. I also don't know what 列式 means; I think it means something like "list formulas for...".

Question: What are the algebraic expressions described by 列式表示比a的5倍大4的数与比a的2倍小3的数 and 列式表示比x的7倍大3的数与比x的6倍小5的数?

It first asks what are the algebraic expressions for 比a的5倍大4的数 and 比a的2倍小3的数, and then compute their sum.

The answer is 5a+4 and 2a-3, summed to 7a+1.

It first asks what are the algebraic expressions for 比x的7倍大3的数 and 比x的6倍小5的数, and then compute their difference. The absolute operation is not needed: the first term is assumed to be the minuend and the second the subtrahend.

The answer is 7x+3 and 6x-5, differenced to x+8.

• List the expressions representing the number of five times "a" plus 4 and the number two times "a" minus 3.

• (5a+4) is the first expression, and (2a-3) is the second expression.

I think this math question can be simplified to:

• 列式並计算 5倍的a大4 和 2倍的a小3 的總和;