readings - How do you read simple arithmetic equations in Japanese?

My dictionary (EN → JP) suggests to translate "Three multiplied by four is twelve" as

3 × 4 = 12

without giving a hint as to how to read this in Japanese.

How do you read simple arithmetic equations (involving only +, –, × and ÷) like the one above in Japanese?

Answer

+: 足{た}す
-: 引{ひ}く
/: 割{わ}る
*: 掛{か}ける

And you just say the terms normally in order. So your example of 3 * 4 = 12 would be ３かける４は１２. Note that = becomes は, similar to how we use "is" in English. As @blutorange mentioned, you can use イコール to mean "equals," however in most situations you'll be good using は.

You learn these things quickly when listening to students recite their 九九{くく}.

For some bonus terminology, you can refer to exponents by using #乗{じょう}, so like ２の二乗は４ or ２の３乗は８. Similarly you can refer to roots with #乗根{じょうこん} (although as @jovanni points out it's normal to use 平方根{へいほうこん} for square roots).