たら / -ば, ...た (counterfactual usage)
文法の解説は英語です。
用法
Vたら/Vば、...た The sentence usually ends with a conjectural expression like のに
例文
もし昨日雨が降っているたら、買い物には出掛けなかっただろう
I probably wouldn't have gone shopping yesterday if it had rained
お金があれば、このパソコンが買えたのに
I could have bought my personal computer if only I had had the money