Im eating around 900 calories a day, mostly veggies , whole grains,and grilled chicken.
I do 30 mins on the elliptical trainer5 days , and do a few at home toning exercises. I also do yoga 30 mins once a week. How long would it take to lose around 25 lbs????
Thanks for looking!!(:
P.s. I am 20 lbs overweight, if that makes any difference on how fast/slow it would happen!!!!!

In general you want to aim to lose around 1-2lbs a week, so ~3 months.

Concentrate on creating a good lifestyle that you can maintain for life. (900 calories is far far too low to be sustainable in the long term. Which means that when you go off the diet you will regain the lost 20lbs and then some since your body will be building up stores for the next "starvation" period.)

I am not a fan of "toning" exercises. Most women (and I'm assuming you are a woman) use weights that are far, far too light. I am a fan (a huge fan) of STRENGTH exercises. (Check with your doctor first).

These is really very good plan to lose weight. Here are some other tips that also helps in losing weight the healthy way:
1 Do exercise like walking, swimming, cycling daily
2 Do Yoga and meditation
3 Drink Green tea or lemon juice it also helps in losing weight
4 Drink plenty of water
5 Eat a balance diet and avoid eating oily food.