Subtraction function

Content

Hi,

Requirement: I want to subtract two value from various response and show in the final response.

Problem: One value coming as string, so I tried to convert as Decimal point. Since I could not use Number (Conversion) function in Subtract, I have used assigned operation and convert as Decimal point. But I got the below error. I noticed, assigned function output also String. 

Response 1

{
  "avlDeposit" : "978409.25"}

Response 2

{
  "holdingAmt" : 409.25
}

How to achieve this?

Got the below error
{
  "type" : "http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.1",
  "title" : "Internal Server Error",
  "detail" : "Internal server error. Please contact oracle support for details.",
  "o:errorCode" : "500",
  "o:errorDetails" : [ {
    "type" : "UnMappedFault:execute",
    "instance" : "<![CDATA[Please inspect the logs for more details. Initiating Request: <request_payload/>\n]]>",
    "title" : "faultName: {{