The rocketpowered X15 reached Mach2 6.7 in 1967.
1967年，以火箭为推进动力的X15曾达到6.7马赫。
A 15 x15 metre square, it ensures sunlight for all the rooms and acts as a kind of green lung.
这个院落只有15乘15平方米，但却能为所有房间提供自然光，并充当一个天然的绿肺。
" Eager Lena quickly shared the offending question (8+29)x15 and was given this helpful tip: "Do the numbers in the parenthesis first so in essence it would be 37 x 15.
急切的莱娜立刻分享了自己的难题：（8+29）x15，她收到了很有用的解题窍门：“先算括号里面的数字，实际上就是37 隦x 15。”
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