using form id's to edit specific forms with css

Hell all

I am currently using form builder in a twenty twelve child theme, I have three forms on the site, I want the text input area to be substantially larger on two of the forms and normal on the other one. So my question is how do I use the form’s id to target specific forms within CSS,
eg. `.vfb-form_id-4 input.vfb-text, input[type=”text”].vfb-text, input[type=”tel”].vfb-text, input[type=”email”].vfb-text, input[type=”url”].vfb-text, textarea.vfb-textarea, select.vfb-select {
font-size: 26px;
font-family: inherit;
line-height: normal;
height: auto;
color: #373737;
margin: 0 0 5px 0;
}`

I cant seem to work it out, I have tried loads of different ways, all to no avail.

Any help would be very much appreciated.

All the best,

Harry

http://ww.wp.xz.cn/extend/plugins/visual-form-builder/