3+6=9英文怎么表达？

很简单，
three plus six equals nine
或者也可以说
the sum of three and six is nine
前者是常用的啦。

相信我啦，“等于”是equal,但是在算式当中是要加S的，就是equals.
另外sum是“和”的意思。

three and six equals nine

three and six make nine
或者是three plus six equals 9

Three plus six equal to nine

three plus six is nine

Three plus six minus nine