Cool, goodluck on your assignment bud. :)
To memorize the irregulars, remember last words, like -é, -emos, <span>-éis, -án. Connect normal irregulars with these words. Boom, you make a future tense irregular.
Estar+emos=estaremos
Vivir+é=viviré</span>
I've been to Mexico and both question 1 and 4 sounds about right. but I would go more with Number 4.
1 ( necesitara ) 2 ( hablara ) 3 ( trabajaras )
21 es la respuesta correcta porque la pregunta traduce a “42 divided by 2” y eso es 21